CVE-2026-41509: Integer underflow in crypto_sign_open() leads to buffer overflow

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-08 · updated 2026-10-26
Weakness: CWE-121

Description

CROSS implementation contains reference and optimized implementations of the CROSS post-quantum signature algorithm. Prior to commit fc6b7e7, there is a buffer overflow in crypto_sign_open() caused by an underflow of the integer mlen. This issue has been patched via commit fc6b7e7.

Affected products

CROSS-signature CROSS-implementation: before 2026-03-23 — fixed in 2026-03-23

How to fix

Upgrade to a fixed version: CROSS-signature CROSS-implementation 2026-03-23. Check the vendor advisory for mitigations.

References

https://github.com/CROSS-signature/CROSS-implementation/commit/fc6b7e78cdf789bb5c395a81dc601356f1383da0
https://github.com/CROSS-signature/CROSS-implementation/security/advisories/GHSA-w72c-hgx8-p7cv

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