CVE-2026-5503
out-of-bounds write in TLSX_EchChangeSNI via attacker-controlled publicName
Summary
out-of-bounds write in TLSX_EchChangeSNI via attacker-controlled publicName
Original description
The description as published by the source.
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.
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-5503 wolfssl
- Ubuntu UBUNTU-CVE-2026-5503 wolfssl
References
- advisory github.com
- advisory nvd.nist.gov
- patch github.com