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High, CVSS 8.6amended

Dulwich: Symlink directory traversal in filter-branch index_filter via cross-commit state persistence

CVE-2026-114097GHSA-5fqc-mrg8-w798

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (dulwich 1.2.8), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI dulwich

    Affected
    >= 0.23.1, <= 1.2.7
    Fixed in
    1.2.8

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.6 · CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
EPSS
  • CVE-2026-114097: 0.19% estimated exploitation activity in the next 30 days; percentile 8.29 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary Dulwich's filterbranch.py CommitFilter.applyindexfilter() is vulnerable to symlink directory traversal. When processing commit history, materialized tree entries (including symlinks) persist in the working directory between commits, allowing a symlink from an ancestor commit to redirect file writes from a descendant commit to arbitrary filesystem locations. Root Cause applyindexfilter() at dulwich/filterbranch.py:212 calls buildindexfromtree(".", tmpindexpath, ...) which materializes all tree entries to the current working directory. The finally block (line 229-230) only cleans up the temporary index file (os.unlink(tmpindexpath)) — NOT the filesystem files written to CWD. When processcommit() processes parents recursively first (line 260), files materialized from ancestor commits persist and affect processing of descendant commits. On dulwich 1.2.7, buildfilefromblob() has no symlink protection, and validatepathelement only validates name patterns, not filesystem state.…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-5fqc-mrg8-w798

  2. Revision 2 · amended ·

    Amended from osv record GHSA-5fqc-mrg8-w798

  3. Revision 1 · created ·

    Published from ghsa record GHSA-5fqc-mrg8-w798

Agent brief

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# Patch Next advisory brief: CVE-2026-114097

Advisory: Dulwich: Symlink directory traversal in filter-branch index_filter via cross-commit state persistence
IDs: CVE-2026-114097, GHSA-5fqc-mrg8-w798
Record: https://patchnext.com/advisories/ghsa-5fqc-mrg8-w798 (revision 3, source checked 26 Oct 2026, 13:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: dulwich 1.2.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI dulwich: affected >= 0.23.1, <= 1.2.7; fixed in 1.2.8

## Suggested inspection (read-only)
- `python -m pip show dulwich`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on dulwich.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5fqc-mrg8-w798 (GitHub-reviewed advisory GHSA-5fqc-mrg8-w798 lists affected ranges: PyPI dulwich >=0.23.1 <=1.2.7)
- Verified: https://osv.dev/vulnerability/GHSA-5fqc-mrg8-w798 (OSV record GHSA-5fqc-mrg8-w798 lists affected ranges: PyPI dulwich >=0.23.1 <1.2.8 (fixed))

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