CVE-2026-5466: wolfSSL

High severity, CVSS 8.1. EPSS: 0.2% chance of exploitation in the next 30 days.

wolfSSL's ECCSI signature verifier `wc_VerifyEccsiHash` decodes the `r` and `s` scalars from the signature blob via `mp_read_unsigned_bin` with no check that they lie in `[1, q-1]`. A crafted forged signature could verify against any message for any identity, using only publicly-known constants.

Affected products

• wolfSSL wolfSSL: before 5.9.1 (fixed in 5.9.1)

Published 2026-04-10. Last modified 2026-06-17.