Prototype Pollution
Detailed paths
Overview
redoc is an OpenAPI/Swagger-generated API Reference Documentation.
Affected versions of this package are vulnerable to Prototype Pollution via the mergeObjects() method in utils/helpers.ts due to improper user input sanitization.
PoC
(async () => {
const lib = await import('redoc');
var BAD_JSON = JSON.parse('{"__proto__":{"polluted":true}}');
var victim = {}
console.log("Before Attack: ", JSON.stringify(victim.__proto__));
try {
lib.mergeObjects ({}, BAD_JSON)
} catch (e) { }
console.log("After Attack: ", JSON.stringify(victim.__proto__));
delete Object.prototype.polluted;
})();
Details
Prototype Pollution is a vulnerability affecting JavaScript. Prototype Pollution refers to the ability to inject properties into existing JavaScript language construct prototypes, such as objects. JavaScript allows all Object attributes to be altered, including their magical attributes such as __proto__, constructor and prototype. An attacker manipulates these attributes to overwrite, or pollute, a JavaScript application object prototype of the base object by injecting other values. Properties on the Object.prototype are then inherited by all the JavaScript objects through the prototype chain. When that happens, this leads to either denial of service by triggering JavaScript exceptions, or it tampers with the application source code to force the code path that the attacker injects, thereby leading to remote code execution.
There are two main ways in which the pollution of prototypes occurs:
Unsafe
Objectrecursive mergeProperty definition by path
Unsafe Object recursive merge
The logic of a vulnerable recursive merge function follows the following high-level model:
merge (target, source)
foreach property of source
if property exists and is an object on both the target and the source
merge(target[property], source[property])
else
target[property] = source[property]
When the source object contains a property named __proto__ defined with Object.defineProperty() , the condition that checks if the property exists and is an object on both the target and the source passes and the merge recurses with the target, being the prototype of Object and the source of Object as defined by the attacker. Properties are then copied on the Object prototype.
Clone operations are a special sub-class of unsafe recursive merges, which occur when a recursive merge is conducted on an empty object: merge({},source).
lodash and Hoek are examples of libraries susceptible to recursive merge attacks.
Property definition by path
There are a few JavaScript libraries that use an API to define property values on an object based on a given path. The function that is generally affected contains this signature: theFunction(object, path, value)
If the attacker can control the value of “path”, they can set this value to __proto__.myValue. myValue is then assigned to the prototype of the class of the object.
Types of attacks
There are a few methods by which Prototype Pollution can be manipulated:
| Type | Origin | Short description |
|---|---|---|
| Denial of service (DoS) | Client | This is the most likely attack. DoS occurs when Object holds generic functions that are implicitly called for various operations (for example, toString and valueOf). The attacker pollutes Object.prototype.someattr and alters its state to an unexpected value such as Int or Object. In this case, the code fails and is likely to cause a denial of service. For example: if an attacker pollutes Object.prototype.toString by defining it as an integer, if the codebase at any point was reliant on someobject.toString() it would fail. |
| Remote Code Execution | Client | Remote code execution is generally only possible in cases where the codebase evaluates a specific attribute of an object, and then executes that evaluation. For example: eval(someobject.someattr). In this case, if the attacker pollutes Object.prototype.someattr they are likely to be able to leverage this in order to execute code. |
| Property Injection | Client | The attacker pollutes properties that the codebase relies on for their informative value, including security properties such as cookies or tokens. For example: if a codebase checks privileges for someuser.isAdmin, then when the attacker pollutes Object.prototype.isAdmin and sets it to equal true, they can then achieve admin privileges. |
Affected environments
The following environments are susceptible to a Prototype Pollution attack:
Application server
Web server
Web browser
How to prevent
Freeze the prototype— use
Object.freeze (Object.prototype).Require schema validation of JSON input.
Avoid using unsafe recursive merge functions.
Consider using objects without prototypes (for example,
Object.create(null)), breaking the prototype chain and preventing pollution.As a best practice use
Mapinstead ofObject.
For more information on this vulnerability type:
Arteau, Oliver. “JavaScript prototype pollution attack in NodeJS application.” GitHub, 26 May 2018
Remediation
Upgrade redoc to version 2.4.0 or higher.
References
Allocation of Resources Without Limits or Throttling
Detailed paths
Overview
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling due to improper parsing of malformed tokens which can lead to memory consumption.
Remediation
Upgrade golang.org/x/oauth2/jws to version 0.27.0 or higher.
References
Server-side Request Forgery (SSRF)
Detailed paths
Overview
golang.org/x/net/http/httpproxy is a package for HTTP proxy determination based on environment variables, as provided by net/http's ProxyFromEnvironment function
Affected versions of this package are vulnerable to Server-side Request Forgery (SSRF) in proxy.go, because hostname matching against proxy patterns may treat an IPv6 zone ID as a hostname component. An environment variable value like *.example.com could be matched to a request intended for [::1%25.example.com]:80.
Remediation
Upgrade golang.org/x/net/http/httpproxy to version 0.36.0 or higher.
References
Allocation of Resources Without Limits or Throttling
Detailed paths
Overview
golang.org/x/crypto/ssh is a SSH client and server
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling in handshakeTransport in handshake.go. An internal queue gets populated with received packets during the key exchange process, while waiting for the client to send a SSH_MSG_KEXINIT. An attacker can cause the server to become unresponsive to new connections by delaying or withholding this message, or by causing the queue to consume all available memory.
Remediation
Upgrade golang.org/x/crypto/ssh to version 0.35.0 or higher.
References
Allocation of Resources Without Limits or Throttling
Detailed paths
Overview
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling due to the use of strings.Split to split JWT tokens. An attacker can cause memory exhaustion and service disruption by sending numerous malformed tokens with a large number of . characters.
Workaround
This vulnerability can be mitigated by pre-validating that payloads passed to Go JOSE do not contain an excessive number of . characters.
Remediation
Upgrade github.com/go-jose/go-jose/v4 to version 4.0.5 or higher.
References
Allocation of Resources Without Limits or Throttling
Detailed paths
Overview
Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling due to the use of strings.Split to split JWT tokens. An attacker can cause memory exhaustion and service disruption by sending numerous malformed tokens with a large number of . characters.
Workaround
This vulnerability can be mitigated by pre-validating that payloads passed to Go JOSE do not contain an excessive number of . characters.
Remediation
Upgrade github.com/go-jose/go-jose/v3 to version 3.0.4 or higher.
References
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Detailed paths
Overview
github.com/Azure/azure-sdk-for-go/sdk/azidentity is a module that provides Microsoft Entra ID (formerly Azure Active Directory) token authentication support across the Azure SDK. It includes a set of TokenCredential implementations, which can be used with Azure SDK clients supporting token authentication.
Affected versions of this package are vulnerable to Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') in the authentication process. An attacker can elevate privileges by exploiting race conditions during the token validation steps. This is only exploitable if the application is configured to use multiple threads or processes for handling authentication requests.
Notes:
An attacker who successfully exploited the vulnerability could elevate privileges and read any file on the file system with SYSTEM access permissions;
An attacker who successfully exploits this vulnerability can only obtain read access to the system files by exploiting this vulnerability. The attacker cannot perform write or delete operations on the files;
The vulnerability exists in the following credential types:
DefaultAzureCredentialandManagedIdentityCredential;The vulnerability exists in the following credential types:
ManagedIdentityApplication (.NET)
ManagedIdentityApplication (Java)
ManagedIdentityApplication (Node.js)
Remediation
Upgrade github.com/Azure/azure-sdk-for-go/sdk/azidentity to version 1.6.0 or higher.
References
- GitHub Commit
- GitHub Commit
- GitHub Commit
- GitHub Commit
- GitHub Commit
- GitHub Commit
- GitHub Commit
- Microsoft Advisory
Regular Expression Denial of Service (ReDoS)
Detailed paths
Overview
foundation-sites is a responsive front-end framework
Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) due to inefficient backtracking in the regular expressions used in URL forms.
PoC
https://www.''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Details
Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.
The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.
Let’s take the following regular expression as an example:
regex = /A(B|C+)+D/
This regular expression accomplishes the following:
AThe string must start with the letter 'A'(B|C+)+The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the+matches one or more times). The+at the end of this section states that we can look for one or more matches of this section.DFinally, we ensure this section of the string ends with a 'D'
The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD
It most cases, it doesn't take very long for a regex engine to find a match:
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total
$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total
The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.
Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.
Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:
- CCC
- CC+C
- C+CC
- C+C+C.
The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.
From there, the number of steps the engine must use to validate a string just continues to grow.
| String | Number of C's | Number of steps |
|---|---|---|
| ACCCX | 3 | 38 |
| ACCCCX | 4 | 71 |
| ACCCCCX | 5 | 136 |
| ACCCCCCCCCCCCCCX | 14 | 65,553 |
By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.
Remediation
There is no fixed version for foundation-sites.
References
Arbitrary Code Injection
Detailed paths
Overview
prismjs is a lightweight, robust, elegant syntax highlighting library.
Affected versions of this package are vulnerable to Arbitrary Code Injection via the document.currentScript lookup process. An attacker can manipulate the web page content and execute unintended actions by injecting HTML elements that overshadow legitimate DOM elements.
Note:
This is only exploitable if the application accepts untrusted input containing HTML but not direct JavaScript.
Remediation
Upgrade prismjs to version 1.30.0 or higher.
References
Insufficient Documentation of Error Handling Techniques
Detailed paths
Overview
Affected versions of this package are vulnerable to Insufficient Documentation of Error Handling Techniques in the ParseWithClaims function. An attacker can exploit this to accept invalid tokens by only checking for specific errors and ignoring others.
Workaround
Users who are not able to upgrade to the fixed version should make sure that they are properly checking for all errors, see example_test.go
Remediation
Upgrade github.com/golang-jwt/jwt/v4 to version 4.5.1 or higher.
References
Insufficient Documentation of Error Handling Techniques
Detailed paths
Overview
Affected versions of this package are vulnerable to Insufficient Documentation of Error Handling Techniques in the ParseWithClaims function. An attacker can exploit this to accept invalid tokens by only checking for specific errors and ignoring others.
Workaround
Users who are not able to upgrade to the fixed version should make sure that they are properly checking for all errors, see example_test.go
Remediation
A fix was pushed into the master branch but not yet published.
References
Cross-site Scripting (XSS)
Detailed paths
Overview
dompurify is a DOM-only XSS sanitizer for HTML, MathML and SVG.
Affected versions of this package are vulnerable to Cross-site Scripting (XSS) due to incorrect handling of template literals in regular expressions. An attacker can manipulate the output of the script by injecting malicious payloads that bypass the dompurify sanitization.
PoC
DOMPurify.sanitize(
`<math><foo-test><mi><li><table><foo-test><li></li></foo-test><a>
<style>
<! \${
</style>
}
<foo-b id="><img src onerror='alert(1)'>">hmm...</foo-b>
</a></table></li></mi></foo-test></math>
`,
{
SAFE_FOR_TEMPLATES: true,
CUSTOM_ELEMENT_HANDLING: {
tagNameCheck: /^foo-/,
},
}
);
Details
A cross-site scripting attack occurs when the attacker tricks a legitimate web-based application or site to accept a request as originating from a trusted source.
This is done by escaping the context of the web application; the web application then delivers that data to its users along with other trusted dynamic content, without validating it. The browser unknowingly executes malicious script on the client side (through client-side languages; usually JavaScript or HTML) in order to perform actions that are otherwise typically blocked by the browser’s Same Origin Policy.
Injecting malicious code is the most prevalent manner by which XSS is exploited; for this reason, escaping characters in order to prevent this manipulation is the top method for securing code against this vulnerability.
Escaping means that the application is coded to mark key characters, and particularly key characters included in user input, to prevent those characters from being interpreted in a dangerous context. For example, in HTML, < can be coded as < and > can be coded as > in order to be interpreted and displayed as themselves in text, while within the code itself, they are used for HTML tags. If malicious content is injected into an application that escapes special characters and that malicious content uses < and > as HTML tags, those characters are nonetheless not interpreted as HTML tags by the browser if they’ve been correctly escaped in the application code and in this way the attempted attack is diverted.
The most prominent use of XSS is to steal cookies (source: OWASP HttpOnly) and hijack user sessions, but XSS exploits have been used to expose sensitive information, enable access to privileged services and functionality and deliver malware.
Types of attacks
There are a few methods by which XSS can be manipulated:
| Type | Origin | Description |
|---|---|---|
| Stored | Server | The malicious code is inserted in the application (usually as a link) by the attacker. The code is activated every time a user clicks the link. |
| Reflected | Server | The attacker delivers a malicious link externally from the vulnerable web site application to a user. When clicked, malicious code is sent to the vulnerable web site, which reflects the attack back to the user’s browser. |
| DOM-based | Client | The attacker forces the user’s browser to render a malicious page. The data in the page itself delivers the cross-site scripting data. |
| Mutated | The attacker injects code that appears safe, but is then rewritten and modified by the browser, while parsing the markup. An example is rebalancing unclosed quotation marks or even adding quotation marks to unquoted parameters. |
Affected environments
The following environments are susceptible to an XSS attack:
- Web servers
- Application servers
- Web application environments
How to prevent
This section describes the top best practices designed to specifically protect your code:
- Sanitize data input in an HTTP request before reflecting it back, ensuring all data is validated, filtered or escaped before echoing anything back to the user, such as the values of query parameters during searches.
- Convert special characters such as
?,&,/,<,>and spaces to their respective HTML or URL encoded equivalents. - Give users the option to disable client-side scripts.
- Redirect invalid requests.
- Detect simultaneous logins, including those from two separate IP addresses, and invalidate those sessions.
- Use and enforce a Content Security Policy (source: Wikipedia) to disable any features that might be manipulated for an XSS attack.
- Read the documentation for any of the libraries referenced in your code to understand which elements allow for embedded HTML.
Remediation
Upgrade dompurify to version 3.2.4 or higher.