CVE-2026-5503
Last modified
CVE-2026-5503 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. 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. EPSS estimates a 0.39% chance of exploitation in the next 30 days.
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/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Wolfssl | Wolfssl | <= 5.9.0 |
References
- https://github.com/wolfSSL/wolfssl/pull/10102Issue Tracking
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
What is CVE-2026-5503?
How severe is CVE-2026-5503?
How do I fix CVE-2026-5503?
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
Related CVEs from 2026
- CVE-2026-55024Access of resource using incompatible type ('type confusion'…7.8
- CVE-2026-55025Access of resource using incompatible type ('type confusion'…7.8
- CVE-2026-55026Integer overflow or wraparound in Microsoft Office allows an…5.5
- CVE-2026-55027Out-of-bounds read in Microsoft Office allows an unauthorize…5.5
- CVE-2026-55028Out-of-bounds read in Microsoft Office allows an unauthorize…5.5
- CVE-2026-55029Heap-based buffer overflow in Microsoft Office Excel allows …7.8
- CVE-2026-55030Improper neutralization of input during web page generation …5.4
- CVE-2026-55031Out-of-bounds read in Microsoft Office Excel allows an unaut…7.8
- CVE-2026-55032Use after free in Microsoft Office Word allows an unauthoriz…7.8
- CVE-2026-55033Integer overflow or wraparound in Microsoft Office Word allo…7.8
- CVE-2026-55034Improper neutralization of input during web page generation …8.7
- CVE-2026-55035Out-of-bounds read in Microsoft Office allows an unauthorize…3.3
Are you affected by CVE-2026-5503?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST