CVE-2026-47712: Dulwich Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-555p-6grf-mh7f",
  "modified" : "2026-06-11T14:07:14Z",
  "published" : "2026-06-08T23:04:48Z",
  "aliases" : [ "CVE-2026-47712" ],
  "summary" : "Dulwich doesn't sanitize commit subjects in `porcelain.format_patch`",
  "details" : "### Impact\n\ndulwich.porcelain.format_patch(outdir=...) derives each patch filename from the commit's subject line. Prior to this fix, get_summary only replaced spaces with dashes - path separators (/, \\),   parent-directory components (..), and   other filename-hostile characters (e.g. :)  were preserved verbatim and passed   straight into os.path.join(outdir,   f\"{i:04d}-{summary}.patch\").\n\nA malicious commit subject could therefore direct the generated patch file outside the requested outdir. Reduced examples:\n\n- x/../../x produced <outdir>/0001-x/../../x.patch, resolving\n  two directories above outdir.\n- x\\..\\..\\x produced the equivalent escape on Windows, here \\ is also a path separator.\n\nRelated issues from the same root cause:\n\n- Subjects containing characters that are illegal in Windows filenames (e.g. :) caused format_patch to fail outright on  Windows, where git would have succeeded.\n- Very long subjects produced excessively long filenames that could exceed filesystem limits; git truncates them.\n\nAnyone calling porcelain.format_patch (or the dulwich format-patch CLI) against untrusted commits - for example, a service that runs format-patch over user-supplied repositories or pull requests - could have patch files written to attacker-chosen locations within the process's write permissions.\n\n### Patches\n\nFixed in Dulwich 1.2.5. Users should upgrade.\n\n dulwich.patch.get_summary now mirrors git's format_sanitized_subject: only `[A-Za-z0-9._]` are kept, runs of other characters collapse to a single -, consecutive . collapse to a single ., trailing ./- are stripped, and the result is length-limited. This makes the returned string safe to embed as a filename component, so format_patch can no longer be steered out of outdir via the commit subject.\n\n###  Workarounds\n\nUntil upgrading, callers that pass untrusted commits to   porcelain.format_patch can:\n\n- Use stdout=True and write the patch to a destination they control, rather than letting format_patch choose the filename.\n- Validate the chosen path before opening - e.g. compare os.path.realpath(returned_path) against  os.path.realpath(outdir) and reject any patch whose resolved path is not inside outdir.\n- Pre-screen commits and refuse to format any whose subject's first line contains /, \\, .., or other characters that are not safe on the target filesystem.\n\n### Resources\n\n- Fix commit: https://github.com/jelmer/dulwich/commit/c2446e51b\n- Affected API: dulwich.porcelain.format_patch / dulwich format-patch\n- Reference behavior: git's format_sanitized_subject in pretty.c",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "dulwich"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.24.0"
      }, {
        "fixed" : "1.2.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/jelmer/dulwich/security/advisories/GHSA-555p-6grf-mh7f"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-47712"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jelmer/dulwich/commit/c2446e51b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jelmer/dulwich"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-08T23:04:48Z",
    "nvd_published_at" : "2026-06-10T23:16:48Z"
  }
}