Rust advisories / libcrux-aesgcm
VulnerabilityRUSTSEC-2026-0211 · libcrux-aesgcm
RUSTSEC-2026-0211: Non-constant time Authentication Tag Check in AES-GCM Decryption
Short answerA security vulnerability in the libcrux-aesgcm crate: Non-constant time Authentication Tag Check in AES-GCM Decryption. No severity score was published. No fixed version: replace the crate or remove the affected code path.
| Crate | libcrux-aesgcm |
|---|---|
| Type | Vulnerability (crypto-failure) |
| Affected versions | Every version. |
| Fixed in | none |
| Severity | not scored 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 |
| Published | 2026-07-14 |
| Last changed | 2026-07-17 |
| Also known as | none |
| Affected functions | libcrux_aesgcm::AesGcm128Key::decrypt, libcrux_aesgcm::AesGcm256Key::decrypt, libcrux_aesgcm::aes_gcm_128::AesGcm128::decrypt, libcrux_aesgcm::aes_gcm_128::Key::decrypt, libcrux_aesgcm::aes_gcm_128::KeyRef::decrypt, libcrux_aesgcm::aes_gcm_128::neon::Key::decrypt, libcrux_aesgcm::aes_gcm_128::neon::KeyRef::decrypt, libcrux_aesgcm::aes_gcm_128::neon::NeonAesGcm128::decrypt, libcrux_aesgcm::aes_gcm_128::portable::Key::decrypt, libcrux_aesgcm::aes_gcm_128::portable::KeyRef::decrypt, libcrux_aesgcm::aes_gcm_128::portable::PortableAesGcm128::decrypt, libcrux_aesgcm::aes_gcm_128::x64::Key::decrypt |
What to do
- Find who pulls it in:
cargo tree -i libcrux-aesgcm. - Avoid the affected API (
libcrux_aesgcm::AesGcm128Key::decrypt,libcrux_aesgcm::AesGcm256Key::decrypt,libcrux_aesgcm::aes_gcm_128::AesGcm128::decrypt,libcrux_aesgcm::aes_gcm_128::Key::decrypt,libcrux_aesgcm::aes_gcm_128::KeyRef::decrypt,libcrux_aesgcm::aes_gcm_128::neon::Key::decrypt), or replace the crate.
Details from the advisory
AES-GCM decryption used an implementation for checking the provided authentication tag against the recomputed authentication tag that was intended to be constant-time, but resulted in non-constant-time code generation in certain circumstances. Note that libcrux-aesgcm does not give guarantees on constant-time code generation and possible mitigations must be considered on a best-effort basis.
Impact
Users of libcrux-aesgcm that expose a decryption oracle to an attacker, which allows repeatedly querying for the same ciphertext were at risk from timing side-channel attacks, depending on their compilation environment. In the worst case, this could lead to recovery of the recomputed authentication tag by the attacker, which enables ciphertext forgery.
Mitigation
Starting from version 0.0.9 (published as libcrux-aes@v0.0.9), AES-GCM decryption uses a different, best-effort constant-time implementation of the tag check, which has been checked to reliably lead to constant time code generation, at the moment.
References
- Package: crates.io/crates/libcrux-aesgcm
- Advisory: rustsec.org/advisories/RUSTSEC-2026-0211.html
- Web: github.com/celabshq/libcrux/pull/1528
From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.
Other advisories for libcrux-aesgcm
Up next
Same cratelibcrux-aesgcm: security historyEvery advisory for this crate, and whether it is safe to use today.Read it next →Did this answer your question?