{"id":"RUSTSEC-2026-0211","aliases":[],"status":"published","title":"Non-constant time Authentication Tag Check in AES-GCM Decryption","description":"AES-GCM decryption used an implementation for checking the provided\nauthentication tag against the recomputed authentication tag that was\nintended to be constant-time, but resulted in non-constant-time code\ngeneration in certain circumstances.\nNote that `libcrux-aesgcm` does not give guarantees on constant-time\ncode generation and possible mitigations must be considered\non a best-effort basis.\n\n## Impact\nUsers of `libcrux-aesgcm` that expose a decryption oracle to an\nattacker, which allows repeatedly querying for the same ciphertext\nwere at risk from timing side-channel attacks, depending on their\ncompilation environment. In the worst case, this could lead to\nrecovery of the recomputed authentication tag by the attacker, which\nenables ciphertext forgery.\n\n## Mitigation\nStarting from version `0.0.9` (published as `libcrux-aes@v0.0.9`),\nAES-GCM decryption uses a different, best-effort constant-time\nimplementation of the tag check, which has been checked to reliably\nlead to constant time code generation, at the moment.","severity":{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","from":"osv"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"published":"2026-07-14T12:00:00Z","modified":"2026-07-17T11:45:03Z","affected":[{"source":"osv","ecosystem":"crates.io","package":"libcrux-aesgcm","ranges":[{"type":"SEMVER","events":[{"introduced":"0.0.0-0"}]}]}],"references":[{"url":"https://crates.io/crates/libcrux-aesgcm","tags":["package"]},{"url":"https://rustsec.org/advisories/RUSTSEC-2026-0211.html","tags":["advisory"]},{"url":"https://github.com/celabshq/libcrux/pull/1528","tags":["web"]}],"sources":{"osv":[{"id":"RUSTSEC-2026-0211","title":"Non-constant time Authentication Tag Check in AES-GCM Decryption","description":"AES-GCM decryption used an implementation for checking the provided\nauthentication tag against the recomputed authentication tag that was\nintended to be constant-time, but resulted in non-constant-time code\ngeneration in certain circumstances.\nNote that `libcrux-aesgcm` does not give guarantees on constant-time\ncode generation and possible mitigations must be considered\non a best-effort basis.\n\n## Impact\nUsers of `libcrux-aesgcm` that expose a decryption oracle to an\nattacker, which allows repeatedly querying for the same ciphertext\nwere at risk from timing side-channel attacks, depending on their\ncompilation environment. In the worst case, this could lead to\nrecovery of the recomputed authentication tag by the attacker, which\nenables ciphertext forgery.\n\n## Mitigation\nStarting from version `0.0.9` (published as `libcrux-aes@v0.0.9`),\nAES-GCM decryption uses a different, best-effort constant-time\nimplementation of the tag check, which has been checked to reliably\nlead to constant time code generation, at the moment.","status":"published","published":"2026-07-14T12:00:00Z","modified":"2026-07-17T11:45:03.695400116Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T15:53:40.430679Z"}]}}