CVE-2026-5188Integer underflow in X.509 SAN parsing in wolfSSL

2.3LowCVSS base score
0.14%Exploitation in 30 daysEPSS · top 97% of all CVEs
NoKnown exploitednot in CISA's KEV catalog
NonePublic exploitsnone known yet

Description

An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.

Timeline

2026
30 Mar 2026
30 Mar 2026
ID reserved
By wolfSSL
10 Apr 202611 days later
10 Apr 2026· 11 days later
Published

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-5188, by who scored it
Scored by	CVSS	Score	Vector
wolfSSLCNA (assigner)	4.0	Low2.3	CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
NVDNVD · Analyzed	4.0	Low2.3	CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/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

EPSS (exploitation in 30 days): 0.14% · top 97% of all CVEs (13 Nov 2026)
CISA SSVC: Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 2.3.

Affected products

wolfSSL · wolfSSL
- affected ≤ 5.9.0

References1

https://github.com/wolfSSL/wolfssl/pull/10024 (opens in a new tab)

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

[![CVE-2026-5188](https://cveledger.app/badge/CVE-2026-5188.svg)](https://cveledger.app/cve/CVE-2026-5188)

Record last updated 10 Apr 2026, 13:41 UTC.