Home/CVE/In TLSX_EchChangeSNI, the ctx-extensions branch set extensions unconditionally even when TLSX_Find returned NULL. This c
CVE

CVE-2026-5503

In TLSX_EchChangeSNI, the ctx-extensions branch set extensions unconditionally even when TLSX_Find returned NULL. This c

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.

CRITICAL · CVSS 9.1 EPSS 0.00053
Schedule remediation
  • SSVC automatable: yes - attacks can be scripted at scale
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-787Out-of-bounds Write
▤

Affected Products & Versions

1
wolfssl<= 5.9.0
▣

Scoring & Timeline

9.1
CRITICAL · CVSS v3.1 · facts@wolfssl.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD09 Apr 2026 · 11:17 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
yes
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

1
msrcCVE-2026-5503
🔗

References & Sources

1
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/wolfSSL/wolfssl/pull/10102Issue Tracking
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