Buffer overflow in Wolfssl
CVE-2026-5503
In TLSX_EchChangeSNI, the ctx->extensions branch set extensions unconditionally even when TLSX_Find returned NULL. This caused TLSX_UseSNI to attach the attacker-controlled publicName to the shared WOLFSSL_CTX when no inner SNI was configured. TLSX_EchRestoreSNI then failed to clean it up because its removal was gated on serverNameX != NULL. The inner ClientHello was sized before the pollution but written after it, causing TLSX_SNI_Write to memcpy 255 bytes past the allocation boundary.
Vulnerability class: Buffer Overflow
EPSS: 0.004 (32.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H.
Affected products
- Wolfssl — versions 0
Weakness classification (CWE)
References
- facts@wolfssl.com (Issue Tracking)
Frequently asked questions
- What is CVE-2026-5503?
- CVE-2026-5503 is a critical-severity vulnerability in Wolfssl, classified under Out-of-bounds Write. CVSS score: 9.1/10. Published 2026-04-09.
- How severe is CVE-2026-5503?
- Critical severity. CVSS v3 base score is 9.1 out of 10.