CVE-2026-5503

CriticalCVSS 9.1/10Last modified Jun 17, 2026

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.

Metrics

CVSS 3.1 9.1/10CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Weakness enumeration

CWE-787

Affected software

No affected versions have been published.

Timeline

Published
Apr 9, 2026
Last modified
Jun 17, 2026
NVD status
Analyzed

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CVE-2026-5503: Critical severity, CVSS 9.1 | Vulnix