Dulwich doesn't sanitize commit subjects in `porcelain.format_patch`
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.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for help- Published
- Jun 10, 2026
- Updated
- Jul 21, 2026
- EPSS
- 0.2% · 7th percentile
- CWE
- CWE-22
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Report tools
Action score
13
Monitor
Low priority for now.
- CVSS
- 13 / 40 · 3.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · GitHub_M
- 3.3
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.
jelmer dulwich
- >= 0.24.0, < 1.2.5affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | dulwich | all versions | — |
| Debian:14 | dulwich | before 1.2.5-1 | 1.2.5-1 |
| openSUSE:Tumbleweed | python-dulwich | before 1.2.5-1.1 | 1.2.5-1.1 |
| PyPI | dulwich | from 0.24.0 · before 1.2.5 | 1.2.5 |
Same product
jelmer: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-42305Dulwich has an arbitrary file write via NTFS-hostile tree entries on Windows35Monitor
- CVE-2026-52726Dulwich's submodule path traversal in porcelain.submodule_update / porcelain.clone(recurse_submodules=True) yields RCE via attacker-dropped .git/hooks payload30Monitor
- CVE-2026-42563Dulwich Vulnerable to Command Injection via Merge Driver Path30Monitor
- CVE-2026-47734Dulwich has unbounded memory allocation in receive-pack from crafted thin packs22Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| debian:dulwich | 1.2.5-1 · Debian:14 | Package registry (OSV) |
| opensuse:python-dulwich | 1.2.5-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| PyPI:dulwich | 1.2.5 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-423050 days apartDulwich has an arbitrary file write via NTFS-hostile tree entries on Windows35Monitor
- CVE-2026-527260 days apartDulwich's submodule path traversal in porcelain.submodule_update / porcelain.clone(recurse_submodules=True) yields RCE via attacker-dropped .git/hooks payload30Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- No account or password is required.
- A user must open a link or visit a page.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- low · data or configuration can be modified
- Availability
- none
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- Low
- Availability impact
- None
Weakness class (CWE)
CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
nvd-secondary
Root cause
A user-supplied file name is joined with the allowed directory, but the result is never checked to confirm it is still inside that directory.
The bug in code
The whole CWE-22 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
const file = path.join(ROOT, req.query.name);res.sendFile(file);Fixed
const file = path.resolve(ROOT, req.query.name);if (!file.startsWith(ROOT + path.sep)) { return res.sendStatus(400);}res.sendFile(file);Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Path TraversalCAPEC-126likelihood: High · Very High
- Using Slashes and URL Encoding Combined to Bypass Validation LogicCAPEC-64likelihood: High · High
- Manipulating Web Input to File System CallsCAPEC-76likelihood: High · Very High
- Using Escaped Slashes in Alternate EncodingCAPEC-78likelihood: High · High
- Using Slashes in Alternate EncodingCAPEC-79likelihood: High · High
ATT&CK techniques
—
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- github.com/jelmer/dulwich/commit/c2446e51b
- github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5
- github.com/jelmer/dulwich/security/advisories/GHSA-555p-6grf-mh7f
Vendor advisories and official records. Exploit/PoC links are deliberately left out.