Incorrect Implementation of Authentication Algorithm
Detailed paths
Overview
golang.org/x/crypto/ssh is a SSH client and server
Affected versions of this package are vulnerable to Incorrect Implementation of Authentication Algorithm when the key passed in the last call before a connection is established is assumed to be the key used for authentication. It is not necessarily the authentication key in use, and this allows attackers who can control the key cache by making their own carefully-timed connections to bypass authorization with subsequent legitimate ServerConfig.PublicKeyCallback
callbacks.
Note: The assumed caching behavior of this callback is not documented and is therefore considered human error, but the project maintainers have observed reliance on it for authorization decisions in production. In fact, the assumption is negated in the documentation, which states "A call to this function does not guarantee that the key offered is in fact used to authenticate." The behavior after upgrading still allows the possibility of an attacker forcing their own key to be the one in the cache when the callback is invoked if the client is using a different authentication method such as PasswordCallback
, KeyboardInteractiveCallback
, or NoClientAuth
. It is therefore recommended to rely on the return values of the connection itself, found in ServerConn.Permissions
for further authorization steps.
Remediation
Upgrade golang.org/x/crypto/ssh
to version 0.31.0 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:
DefaultAzureCredential
andManagedIdentityCredential
;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:
A
The 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.D
Finally, 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
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.