CVE•Published 2026-04-09•Modified 2026-04-27•1 article on news•6 live references•NVD data

CVE-2026-5503Wolfssl · Wolfssl

Vulnerability data via NVD (ingested)

CVSS v3.1

9.1

CRITICAL

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

EPSS percentile

Exploit Prediction Scoring System · top 83% of all CVEs

Weaknesses (CWE)

CWE-787Out-of-bounds Write

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.

Timeline

Published 2026-04-09

Modified 2026-04-27

External references

NVD MITRE Exploit-DB GitHub PoC Sploitus VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag0 hosts

vuln:CVE-2026-5503

Hosts Shodan has explicitly fingerprinted as vulnerable.

Shodan · product

product:"Wolfssl Wolfssl"

All exposed Wolfssl Wolfssl instances — cross-reference with the CVE's affected-version range.

Shodan · banner/body mention

http.html:"Wolfssl"

HTTP body or banner mentions "Wolfssl" — catches deploys Shodan didn't identify as a product.

More intel sources (5)

Shodan report

vuln:CVE-2026-5503