CVE-2026-3849: wolfSSL

Critical severity, CVSS 9.8. EPSS: 0.8% chance of exploitation in the next 30 days.

Stack Buffer Overflow in wc_HpkeLabeledExtract via Oversized ECH Config. A vulnerability existed in wolfSSL 5.8.4 ECH (Encrypted Client Hello) support, where a maliciously crafted ECH config could cause a stack buffer overflow on the client side, leading to potential remote execution and client program crash. This could be exploited by a malicious TLS server supporting ECH. Note that ECH is off by default, and is only enabled with enable-ech.

Affected products

• wolfSSL wolfSSL: from 5.6.0, before 5.9.0 (fixed in 5.9.0)

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