What’s Vulnerable › Vulnerabilities
CVE-2026-5503: out-of-bounds write in TLSX_EchChangeSNI via attacker-controlled publicName
- Severity: critical (CVSS 9.1 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.5% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-04-09 · updated 2026-06-17
- Weakness: CWE-787
Description
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.
Affected products
- wolfSSL: through 5.9.0
References
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