CVE-2026-47712 Dulwich doesn't sanitize commit subjects in `porcelain.format_patch`
Attackers can write patch files outside the intended directory via malicious commit subjects in Dulwich's format_patch function.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-47712?
CVE-2026-47712 is a low-severity path traversal vulnerability in jelmer dulwich, published on 10 Jun 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
Dulwich is a pure-Python implementation of the Git file formats and protocols. Starting in version 0.24.0 and prior to version 1.2.5, 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. This is fixed in Dulwich 1.2.5. Users should upgrade to 1.2.5 or later. 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. 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; and/or 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.
Weakness: CWE-22
Which versions are affected by CVE-2026-47712?
3 open source packages ship an affected version, including dulwich.
| Package | Affected | Fixed in |
|---|---|---|
dulwich PyPI | From 0.24.0 | 1.2.5 |
dulwich PyPI | From 0.24.0 | 1.2.5 |
dulwich PyPI | From 0.24.0 | 1.2.5 |
How do I fix CVE-2026-47712?
Upgrade dulwich to 1.2.5 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-47712 being exploited?
There is no known exploitation of CVE-2026-47712 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-UA20126, CLSA-2026-1784164011, DEBIAN-CVE-2026-47712, ECHO-5850-4d68-024e, GHSA-555p-6grf-mh7f, MINI-x6q7-pwp4-w446 and 2 more.