# CVE-2026-104254: liboqs out-of-bounds read in HSS/LMS signature verification

Source: https://junglewise.ai/threats/cve-2026-104254-liboqs-is-a-c-language-cryptographic-library-that-provides  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-06. Updated: 2026-11-06  
License: CC BY 4.0 with a link back

CVE-2026-104254 · Severity: medium · CVSS 5.3 · Published 2026-11-06

liboqs is a C cryptographic library implementing post-quantum algorithms. When verifying HSS-LMS signatures with truncated or malformed input, the library reads up to 32 bytes beyond the caller's buffer, causing a possible crash or denial of service. An attacker need only provide a plausibly-formatted public key and truncated signature to trigger the vulnerability; no valid signature is required.

Technologies: [Open Quantum Safe Liboqs](https://junglewise.ai/threats/technologies/liboqs). Vendors: [Open Quantum Safe](https://junglewise.ai/threats/vendors/open-quantum-safe).

## Quick answers

**Is CVE-2026-104254 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-104254 being exploited in the wild.

**How severe is CVE-2026-104254?** Medium severity, with a CVSS score of 5.3, published 6 November 2026.

**Which products and versions are affected?** Open Quantum Safe Liboqs 0.11.0 through 0.16.0.

**Is there a fix for CVE-2026-104254?** Yes: fixed in 0.17.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-104254 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-104254?** Check whether you run Open Quantum Safe Liboqs 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.

## How to fix

- Fixed in 0.17.0

## Technical details

Out-of-bounds read in hss_validate_signature_init() and is_hss_public_key() in the LMS signature verification path (src/sig_stfl/lms/external/hss_verify_inc.c) when OQS_ENABLE_SIG_STFL_LMS=ON. The vulnerability occurs because length checks enforce only a 4-byte minimum before parsing a 12-byte header and reading the LM-OTS randomizer field; an attacker-controlled truncated signature reaches the verification functions with fully attacker-controlled bytes. The read data is processed only by internal hash operations and not disclosed; impact is verifier crash and denial of service.

## Affected products

- Open Quantum Safe liboqs 0.11.0 through 0.16.0

## Timeline

- 2026-11-06: disclosed: CVE-2026-104254 published
- 2026-09-09: patched: Fix merged in PR #2507

## References

- [https://github.com/open-quantum-safe/liboqs/commit/df3eb80fe68d2e5db0ecf5d503082cd5699e0859](https://github.com/open-quantum-safe/liboqs/commit/df3eb80fe68d2e5db0ecf5d503082cd5699e0859)
- [https://github.com/open-quantum-safe/liboqs/pull/2507](https://github.com/open-quantum-safe/liboqs/pull/2507)

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