Public bug reported: [Impact] The libssh library in Ubuntu 24.04 LTS (0.10.6) has a bug where key exchange (kex) initialization can generate a trailing comma in the default cipher list under specific build or runtime configurations. This trailing comma leads to unexpected parsing behaviors, minor syntax errors, or handshake failures when interacting with strict SSH clients or servers that do not tolerate malformed cipher strings.
The upstream project fixed this by restructuring how cipher substrings are concatenated, avoiding the trailing comma altogether. [Test Plan] 1. Install libssh-4 from the standard noble repositories. 2. Run an application utilizing libssh key exchange initialization or query the default ciphers programmatically using `ssh_kex_get_default_methods(SSH_CRYPT_C_S)`. 3. Observe that the returned cipher string incorrectly ends with a trailing comma (or requires automated string truncation workarounds). 4. Apply the patch, rebuild, and re-run. The cipher list string should now be cleanly formatted without any trailing commas. [Where problems could occur] The patch modifies 'src/kex.c' and updates the unit tests in 'tests/unittests/torture_config.c'. The risk is low because it strictly changes macro definitions for string concatenation during cipher initialization. It does not alter the actual list of supported ciphers, cryptographic logic, or API signatures. The modification is short, isolated, and verified by upstream unit tests. [Other Info] Upstream commit: https://gitlab.com/libssh/libssh-mirror/-/commit/a8b7e17aa0cb51a62f308af0bb456a26d461234e Author: Jakub Jelen <[email protected]> ** Affects: libssh (Ubuntu) Importance: Undecided Status: New ** Tags: noble sru -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2162736 Title: SRU: libssh trailing comma in cipher list causing kex generation anomalies To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/libssh/+bug/2162736/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
