# CVE-2026-104254: liboqs: Heap out-of-bounds read in LMS/HSS signature verification via unvalidated signature length (hss_verify_inc.c:215)

Status: published. Published: 2026-11-06. Updated: 2026-11-06.

liboqs is a C-language cryptographic library that provides implementations of post-quantum cryptography algorithms. From 0.11.0 through 0.16.0, builds configured with OQS_ENABLE_SIG_STFL_LMS=ON can read beyond a caller-supplied signature buffer when an untrusted truncated LMS or HSS-LMS signature reaches OQS_SIG_STFL_verify or OQS_SIG_STFL_alg_lms_verify. In hss_validate_signature_init() in src/sig_stfl/lms/external/hss_verify_inc.c, consumed-length checks do not ensure that the bottom-level q and C fields remain available, allowing up to 32 bytes to be read past the buffer. In version 0.16.0, is_hss_public_key() also reads at offset 8 after only a four-byte length check, allowing an over-read of up to eight bytes. No valid signature is required, but the public key must be syntactically plausible. The read data is consumed only by an internal hash and is not exposed, so the supported impact is a possible verifier crash and denial of service, not memory disclosure or acceptance of an invalid signature. This issue is scheduled to be fixed in version 0.17.0.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- open-quantum-safe / liboqs: >= 0.11.0, <= 0.16.0 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-125

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/open-quantum-safe/liboqs/security/advisories/GHSA-wh5q-mpc8-67wf (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/open-quantum-safe/liboqs/pull/2507 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/open-quantum-safe/liboqs/commit/df3eb80fe68d2e5db0ecf5d503082cd5699e0859 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-104254; retrieved 2026-11-06; source updated 2026-11-06

Revision: 9a37f54eda38d703e8d217a7ff7c6310db99a312e630fb4e74d4d94699e9fc4d

Canonical: https://y2.dev/cve/CVE-2026-104254

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