# pqc_kyber Rust library unmaintained with unpatched flaw

Source: https://junglewise.ai/threats/rustsec-2026-0289-pqc-kyber-is-unmaintained-e19367b2  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-17. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

Severity: info · Published 2026-09-17

The pqc_kyber Rust library, which implements post-quantum cryptography for securing communications, has not been updated since August 2023 and is no longer maintained by its developers. An unpatched vulnerability exists in the AVX2 hardware-accelerated backend that could allow attackers to recover encryption keys through a chosen-ciphertext attack. Applications using this library for cryptographic protection are at risk of data exposure if the vulnerable code paths are exercised.

Technologies: [pqc_kyber (crates.io)](https://junglewise.ai/threats/technologies/pqc-kyber). Vendors: [crates.io](https://junglewise.ai/threats/vendors/crates-io).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Informational severity, published 17 September 2026.

**Which products and versions are affected?** Argyle Software Pqc Kyber all versions including 0.7.1; pqc_kyber (crates.io) SEMVER:introduced=0.0.0-0.

**Is there a fix for This vulnerability?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected?** Check whether you run Argyle Software Pqc Kyber or pqc_kyber (crates.io) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

pqc_kyber is an unmaintained Rust implementation of ML-KEM (Kyber) post-quantum cryptography. A chosen-ciphertext key-recovery flaw exists in the AVX2 backend, with a fix proposed in an open pull request (Argyle-Software/kyber#121) that has not been reviewed or merged. The maintainer is unresponsive and no patched versions have been released since 0.7.1 (2023-08-23).

## Affected products

- Argyle Software pqc_kyber all versions including 0.7.1

## Timeline

- 2026-09-17: disclosed: Advisory published

## References

- [https://crates.io/crates/pqc_kyber](https://crates.io/crates/pqc_kyber)
- [https://rustsec.org/advisories/RUSTSEC-2026-0289.html](https://rustsec.org/advisories/RUSTSEC-2026-0289.html)

## Related threats

- [RUSTSEC-2026-0290 - pqc_kyber: AVX2 backend skips Fujisaki-Okamoto implicit rejection, enabling chosen-ciphertext key recovery](https://junglewise.ai/threats/rustsec-2026-0290-pqc-kyber-avx2-backend-skips-fujisaki-okamoto-5f69a5b0)
- [pqc_kyber KyberSlash: division timings depending on secrets](https://junglewise.ai/threats/pqc-kyber-kyberslash-division-timings-depending-on-secrets-93d94e36)
- [RUSTSEC-2023-0079 - KyberSlash: division timings depending on secrets](https://junglewise.ai/threats/rustsec-2023-0079-kyberslash-division-timings-depending-on-secrets-6aa36d51)