rsync through 3.5.1 Denial of Service via hash_search() Checksum Collisions

Summary

rsync through 3.5.1 contains a denial of service vulnerability in the delta-transfer sender's hash_search() in match.c that allows malicious receivers to trigger unbounded strong-checksum work at consecutive offsets. Unauthenticated attackers pulling from a public daemon module can supply weak checksums colliding with consecutive rolling windows plus non-matching strong checksums, exhausting sender CPU across concurrent connections.

Remediation

1. Inventory every RsyncProject rsync deployment, including staging.
2. No fixed version appears in the public sources yet. Check the references below and the vendor directly.

References

• Patchhttps://github.com/RsyncProject/rsync/pull/1132
• Patchhttps://github.com/RsyncProject/rsync/commit/a7404a9a633cff28ee1602f328b9c3fa69cdbd04
• Advisoryhttps://www.vulncheck.com/advisories/rsync-through-3.5.1-denial-of-service-via-hash-search-checksum-collisions
• Referencehttps://github.com/RsyncProject/rsync
• Referencehttps://github.com/RsyncProject/rsync/blob/a7404a9a633cff28ee1602f328b9c3fa69cdbd04/testsuite/hashsearch-collision-skip_test.py