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GHSA-rv6r-3f5q-9rgx

Twisted SSH client and server deny of service during SSH handshake.

Source: GitHub Advisory Database (reviewed) High CVE-2022-21716

Packages

EcosystemPackageAffectedFixed in
PyPI twisted >= 21.7.0, < 22.2.0 22.2.0

Details

As written in the advisory (Markdown source, shown as plain text).

### Impact The Twisted SSH client and server implementation naively accepted an infinite amount of data for the peer's SSH version identifier. A malicious peer can trivially craft a request that uses all available memory and crash the server, resulting in denial of service. The attack is as simple as `nc -rv localhost 22 < /dev/zero`. ### Patches The issue was fix in GitHub commit https://github.com/twisted/twisted/commit/98387b39e9f0b21462f6abc7a1325dc370fcdeb1 A fix is available in Twisted 22.2.0. ### Workarounds * Limit access to the SSH server only to trusted source IP addresses. * Connect over SSH only to trusted destination IP addresses. ### References Reported at https://twistedmatrix.com/trac/ticket/10284 Discussions at https://github.com/twisted/twisted/security/advisories/GHSA-rv6r-3f5q-9rgx ### For more information Found by vin01

References

External links from the advisory. They lead to third-party sites.