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GHSA-qjwp-hrq6-r26r
kasImpact
When relying solely on a git commit ID (SHA-1 or SHA-256) to qualify if a checkout of a repository is equivalent to the state validated while adding its commit ID to a kas configuration, users may be tricked to check out a branch of the same name from this repository. This implies that the referenced repository has been taken over by an attacker and modified to carry such a branch. SHA-1 commits may also be replaced by creating hash collisions, so the primary impact of this issue is on SHA-256 commit IDs.
Patches
Commit https://github.com/siemens/kas/commit/4cb4a3d01122ffaec9feaae768a5814092f6f9b5 is resolving this issue. It has been released along with kas version 5.3.
Workarounds
Avoid relying solely on the commit ID for integrity validation of a repository that might become under control of a malicious 3rd party. If available, additional validate cryptographically signed commits or tags. Alternatively, mirror the repository to a save place, validate its integrity, and use this instead of the original one.
Credits
That such issues exist was already reported 3 years ago by Aditya Sirish A Yelgundhalli. At this point, no strong integrity checks for external repositories were in place in kas, and Siemens stated in the kas documentation that such attacks are considered out of scope. This hasn't changed for SHA-1 commits as explained above. If a repo provides SHA-256 commits, though, those may be considered strong enough (even if not providing authenticity proof) and can be affected by this issue.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker needs basic access or low-level privileges.
Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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