Conflibot: Command injection via crafted pull request branch names under pull_request_target

{
  "id": "0ddcacf7a48438c354a7ae185a7d035788f37e474a0770679609e7d3bcb667f7",
  "url": "https://osv.dev/vulnerability/CVE-2026-55158",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Conflibot: Command injection via crafted pull request branch names under pull_request_target",
    "summary": "Conflibot warns in advance when merging a pull request will cause conflicts in other open pull requests. Prior to 1.2.1, src/index.ts builds git checkout, git merge, and git format-patch commands by interpolating the attacker-controlled pull request head.ref value into strings passed to exec. In the documented pull_request_target configuration, an attacker can open a pull request, including from a fork, whose branch name contains shell metacharacters, and the workflow automatically interprets those characters as commands without maintainer interaction. The commands execute on a runner with base-repository secrets and a write-scoped GITHUB_TOKEN, allowing arbitrary command execution, secret or token exfiltration, unauthorized pushes, and other token abuse. The fixed implementations in src/index.ts and src/conflibot.ts use execFile or spawn argument arrays, and the v2 line also uses numeric pull-request refs rather than branch names. This issue is fixed in versions 1.2.1 and 2.0.0.",
    "evidence": "osv:CVE-2026-55158",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-55158",
      "aliases": [
        "CVE-2026-55158",
        "GHSA-2qvg-qr73-mqxp"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/wktk/conflibot",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "59e255c49c920fd6b67471ab9ef3bf194439a3f2"
                },
                {
                  "fixed": "0107ac6a4575ea200d0b92287ea58f975be9505d"
                },
                {
                  "fixed": "401bde09ac47fb11375ecf9fb663970532995776"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.2.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "0107ac6a4575ea200d0b92287ea58f975be9505d"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "59e255c49c920fd6b67471ab9ef3bf194439a3f2"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "59e255c49c920fd6b67471ab9ef3bf194439a3f2"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v1.2.1"
                  },
                  {
                    "range": [
                      {
                        "fixed": "401bde09ac47fb11375ecf9fb663970532995776"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v2.0.0"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.2.0",
            "v1.1.2-pre2",
            "v1.1.2-pre1",
            "v1.1.1",
            "v1.1.0",
            "v1.0.1",
            "v1.0.0",
            "v0.3.0",
            "v0.2.0",
            "v0.1.0",
            "v0.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55158.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:33.602973364Z",
      "provider": "osv",
      "references": [
        "https://github.com/wktk/conflibot/releases/tag/v1.2.1",
        "https://github.com/wktk/conflibot/releases/tag/v2.0.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55158.json",
        "https://github.com/wktk/conflibot/security/advisories/GHSA-2qvg-qr73-mqxp",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-55158",
        "https://github.com/wktk/conflibot/commit/0107ac6a4575ea200d0b92287ea58f975be9505d",
        "https://github.com/wktk/conflibot/commit/59e255c49c920fd6b67471ab9ef3bf194439a3f2",
        "https://github.com/wktk/conflibot/pull/329"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-78"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55158.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-55158",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 500991,
  "published_at": "2026-09-15T14:47:58.804+00:00"
}