CVE-2026-5503
out-of-bounds write in TLSX_EchChangeSNI via attacker-controlled publicName
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.
CVSS Vector Breakdown
AV:NAttack VectorAC:LAttack ComplexityPR:NPrivileges RequiredUI:NUser InteractionS:UScopeC:NConfidentialityI:HIntegrityA:HAvailabilityWeaknesses
Affected Products
Attack Graph
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Exploitability
MITRE ATT&CK
2 techniquesReferences
Timeline
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