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CVE-2026-5503 Details

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.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:9.1 CRITICALVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/wolfSSL/wolfssl/pull/10102	[email protected]	Issue Tracking

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-787	Out-of-bounds Write	[email protected]

Affected Products

Product	Versions
wolfssl wolfssl	<= 5.9.0
CPE cpe:2.3:a:wolfssl:wolfssl:::::::: Remediation No remediation found in references.

Change History

4 change records found show changes

Date	Action	Recorded By
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
Apr 27, 2026	Initial Analysis	[email protected]
Apr 9, 2026	New CVE Received	[email protected]