CVE-2026-3549: wolfSSL

Critical severity, CVSS 9.8. EPSS: 0.6% chance of exploitation in the next 30 days.

Heap Overflow in TLS 1.3 ECH parsing. An integer underflow existed in ECH extension parsing logic when calculating a buffer length, which resulted in writing beyond the bounds of an allocated buffer. Note that in wolfSSL, ECH is off by default, and the ECH standard is still evolving.

Affected products

• wolfSSL wolfSSL: before 5.9.0 (fixed in 5.9.0)

Published 2026-03-19. Last modified 2026-06-17.