Security advisory

{
  "id": "cabd61fa218d1f7fd481b7751636875d06e38e3f152889cf8bdcbe7fb9b30c60",
  "url": "https://osv.dev/vulnerability/CVE-2020-24240",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2020-24240",
    "summary": "GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when a '\\0' byte is encountered. NOTE: there is a risk only if Bison is used with untrusted input, and the observed bug happens to cause unsafe behavior with a specific compiler/architecture. The bug report was intended to show that a crash may occur in Bison itself, not that a crash may occur in code that is generated by Bison.",
    "evidence": "osv:CVE-2020-24240",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2020-24240",
      "aliases": [
        "CVE-2020-24240"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/akimd/bison",
              "type": "GIT",
              "events": [
                {
                  "introduced": "6675d36e2531f2573dcb8944bd9877214677e151"
                },
                {
                  "last_affected": "6675d36e2531f2573dcb8944bd9877214677e151"
                },
                {
                  "fixed": "be95a4fe2951374676efc9454ffee8638faaf68d"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:gnu:bison:3.7:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "3.7"
                      },
                      {
                        "last_affected": "3.7"
                      }
                    ],
                    "source": "CPE_STRING"
                  },
                  {
                    "range": [
                      {
                        "fixed": "be95a4fe2951374676efc9454ffee8638faaf68d"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.7",
            "v3.7"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2020-24240.json",
            "vanir_signatures": [
              {
                "id": "CVE-2020-24240-85d57cd5",
                "digest": {
                  "threshold": 0.9,
                  "line_hashes": [
                    "152892177091449443900596977177214106375",
                    "110470093975942762776580447940415453127",
                    "8556976720912662219078527567889747895"
                  ]
                },
                "source": "https://github.com/akimd/bison/commit/be95a4fe2951374676efc9454ffee8638faaf68d",
                "target": {
                  "file": "src/flex-scanner.h"
                },
                "deprecated": false,
                "signature_type": "Line",
                "signature_version": "v1"
              }
            ],
            "vanir_signatures_modified": "2026-10-20T13:56:57Z"
          }
        }
      ],
      "modified": "2026-10-20T13:56:57.467927917Z",
      "provider": "osv",
      "references": [
        "https://github.com/akimd/bison/compare/v3.7...v3.7.1",
        "https://lists.gnu.org/r/bug-bison/2020-07/msg00051.html",
        "https://github.com/akimd/bison/commit/be95a4fe2951374676efc9454ffee8638faaf68d"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2020-24240",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 388441,
  "published_at": "2020-08-25T14:15:16.543+00:00"
}