PYSEC-2026-2462
Vulnerability from pysec - Published: 2026-07-13 15:46 - Updated: 2026-07-13 16:03
VLAI
Details
Impact
dulwich.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").
A malicious commit subject could therefore direct the generated patch file outside the requested outdir. Reduced examples:
- x/../../x produced /0001-x/../../x.patch, resolving two directories above outdir.
- x....\x produced the equivalent escape on Windows, here \ is also a path separator.
Related issues from the same root cause:
- Subjects containing characters that are illegal in Windows filenames (e.g. :) caused format_patch to fail outright on Windows, where git would have succeeded.
- Very long subjects produced excessively long filenames that could exceed filesystem limits; git truncates them.
Anyone 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.
Patches
Fixed in Dulwich 1.2.5. Users should upgrade.
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.
Workarounds
Until upgrading, callers that pass untrusted commits to porcelain.format_patch can:
- Use stdout=True and write the patch to a destination they control, rather than letting format_patch choose the filename.
- 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.
- 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.
Resources
- Fix commit: https://github.com/jelmer/dulwich/commit/c2446e51b
- Affected API: dulwich.porcelain.format_patch / dulwich format-patch
- Reference behavior: git's format_sanitized_subject in pretty.c
Severity
Impacted products
| Name | purl | dulwich | pkg:pypi/dulwich |
|---|
Aliases
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "dulwich",
"purl": "pkg:pypi/dulwich"
},
"ranges": [
{
"events": [
{
"introduced": "0.24.0"
},
{
"fixed": "1.2.5"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.24.0",
"0.24.1",
"0.24.10",
"0.24.2",
"0.24.3",
"0.24.4",
"0.24.5",
"0.24.6",
"0.24.7",
"0.24.8",
"0.24.9",
"0.25.0",
"0.25.1",
"0.25.2",
"1.0.0",
"1.1.0",
"1.2.0",
"1.2.1",
"1.2.2",
"1.2.3",
"1.2.4"
]
}
],
"aliases": [
"CVE-2026-47712",
"GHSA-555p-6grf-mh7f"
],
"details": "### Impact\n\ndulwich.porcelain.format_patch(outdir=...) derives each patch filename from the commit\u0027s 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 \u003coutdir\u003e/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\u0027s write permissions.\n\n### Patches\n\nFixed in Dulwich 1.2.5. Users should upgrade.\n\n dulwich.patch.get_summary now mirrors git\u0027s 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\u0027s 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\u0027s format_sanitized_subject in pretty.c",
"id": "PYSEC-2026-2462",
"modified": "2026-07-13T16:03:57.395315Z",
"published": "2026-07-13T15:46:15.563670Z",
"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"
},
{
"type": "PACKAGE",
"url": "https://pypi.org/project/dulwich"
},
{
"type": "ADVISORY",
"url": "https://github.com/advisories/GHSA-555p-6grf-mh7f"
}
],
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "Dulwich doesn\u0027t sanitize commit subjects in `porcelain.format_patch`"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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