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Integer underflow in X.509 SAN parsing in wolfSSL

Type: advisorySources: OSV

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.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-5188
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 18:32 UTC · Revision 1

Source evidence

Integer underflow in X.509 SAN parsing in wolfSSL

core-osv · Original source

Published 10 Apr 2026, 03:24 UTC

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.

osv:CVE-2026-5188
Complete source record
{
  "id": "5d9e469392302ad918f161649c8dbb3fed49ecd5d69520f066e885642e22e46f",
  "url": "https://osv.dev/vulnerability/CVE-2026-5188",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Integer underflow in X.509 SAN parsing in wolfSSL",
    "summary": "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.",
    "evidence": "osv:CVE-2026-5188",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CVE-2026-5188",
      "aliases": [
        "CVE-2026-5188"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/wolfssl/wolfssl",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1d363f3adceba9d1478230ede476a37b0dcdef24"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "5.9.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "cpe": "cpe:2.3:a:wolfssl:wolfssl:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "5.9.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v5.9.0-stable",
            "v5.8.4-stable",
            "wolfEntropy2d",
            "v5.8.2-stable",
            "wolfEntropy1",
            "v5.8.0-stable",
            "v5.7.6-stable",
            "v5.7.4-stable",
            "v5.2.1",
            "v5.7.2-stable",
            "v5.7.0-stable",
            "v5.6.6-stable",
            "v5.6.4-stable",
            "WCv5.0-RC12",
            "WCv5.0-RC11",
            "WCv5.0-RC10",
            "v5.6.2-stable",
            "v5.6.3-stable",
            "v5.6.0-stable",
            "v5.5.4-stable",
            "v5.5.3-stable",
            "v5.5.2-stable",
            "v5.5.1-stable",
            "v5.5.0-stable",
            "v5.4.0-stable",
            "v5.3.0-stable",
            "v5.2.0-stable",
            "v5.1.0-stable",
            "v5.0.0-stable",
            "WCv5.0-RC9",
            "v4.8.0-stable",
            "v4.7.1r",
            "v4.7.0-stable",
            "v4.6.0-stable",
            "v4.5.0-stable",
            "v4.4.0-stable",
            "v4.3.0-stable",
            "v4.2.0c",
            "v4.2.0-stable",
            "v4.1.0-stable",
            "v4.0.0-stable",
            "list",
            "v3.15.7-stable",
            "v3.15.6",
            "v3.15.5a",
            "v3.15.5-stable",
            "WCv4-rng-stable",
            "v3.15.3-stable",
            "l",
            "v3.15.0-stable",
            "v3.14.4",
            "v3.14.2",
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            "v3.13.3",
            "v3.13.2",
            "v3.13.0-stable",
            "v3.12.2-stable",
            "v3.12.0-stable",
            "v3.11.1-tls13-beta",
            "v3.11.0-stable",
            "v3.10.3",
            "v3.10.2-stable",
            "v3.10.0a",
            "v3.10.0-stable",
            "v3.9.10b",
            "v3.9.10-stable",
            "v3.9.8",
            "v3.9.6w",
            "v3.9.6",
            "v3.9.1",
            "v3.9.0",
            "v3.8.0",
            "v3.7.3",
            "v3.7.1",
            "v3.7.0",
            "v3.6.9",
            "v3.6.8",
            "v3.4.6",
            "v3.4.2",
            "v3.4.0",
            "v3.3.3",
            "v3.3.0",
            "v3.2.6",
            "v3.2.4",
            "v3.2.0",
            "v2.9.4",
            "v2.9.2",
            "v2.9.1",
            "v0.5",
            "v2.9.0",
            "v2.8.6",
            "v2.8.5a",
            "v2.8.5",
            "v2.8.4",
            "v2.8.3",
            "v2.8.2",
            "v2.8.0",
            "v2.7.2",
            "v2.7.0",
            "v2.6.2",
            "v2.6.0",
            "v2.4.7",
            "v2.4.6",
            "v2.4.2",
            "v2.0.8",
            "v2.0.6",
            "v2.0.3",
            "v2.0.2",
            "v2.0rc3",
            "v2.0rc2b",
            "v2.0rc2",
            "v2.0rc1",
            "v1.9.0",
            "v1.8.8.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-5188.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:38.231981969Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5188.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-5188",
        "https://github.com/wolfSSL/wolfssl/pull/10024",
        "https://github.com/wolfSSL/wolfssl"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-191"
        ],
        "cna_assigner": "wolfSSL",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5188.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-5188",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 505727,
  "published_at": "2026-04-10T03:24:21.126+00:00"
}