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High, CVSS 8.6amended

Dulwich: Symlink write-through in checkout(paths=[]) via raw os.open bypasses all symlink protections

CVE-2026-114096GHSA-8w8g-wq8h-fq33

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
    >= 0.24.0, <= 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-2026-114096: 0.15% estimated exploitation activity in the next 30 days; percentile 4.63 (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 porcelain.checkout(paths=[...]) code path writes files using raw os.open(filepath, OWRONLY|OCREAT|OTRUNC, mode) followed by f.write(obj.data). This code path does NOT call buildfilefromblob() at all, completely bypassing any symlink protections (including the unreleased d09f8af fix). os.open without ONOFOLLOW follows symlinks at both the target file and intermediate directories, allowing arbitrary file writes. Root Cause At dulwich/porcelain/init.py:5661-5675, the checkout(paths=[...]) implementation: checkedworktreepath() (line 601-631) only performs name validation — checking that the path doesn't start with / or \\ and that components pass INVALIDDOTNAMES checks. It performs zero filesystem symlink detection. Impact An attacker can craft a malicious repository that, when a victim clones it and runs checkout(paths=[...]), writes attacker-controlled content (with attacker-controlled permissions) to any filesystem location accessible to the user. Writing to…

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

    Amended from ghsa record GHSA-8w8g-wq8h-fq33

  2. Revision 2 · amended ·

    Amended from osv record GHSA-8w8g-wq8h-fq33

  3. Revision 1 · created ·

    Published from ghsa record GHSA-8w8g-wq8h-fq33

Agent brief

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# Patch Next advisory brief: CVE-2026-114096

Advisory: Dulwich: Symlink write-through in checkout(paths=[]) via raw os.open bypasses all symlink protections
IDs: CVE-2026-114096, GHSA-8w8g-wq8h-fq33
Record: https://patchnext.com/advisories/ghsa-8w8g-wq8h-fq33 (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 >= 0.24.0, <= 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-8w8g-wq8h-fq33 (GitHub-reviewed advisory GHSA-8w8g-wq8h-fq33 lists affected ranges: PyPI dulwich >=0.24.0 <=1.2.7)
- Verified: https://osv.dev/vulnerability/GHSA-8w8g-wq8h-fq33 (OSV record GHSA-8w8g-wq8h-fq33 lists affected ranges: PyPI dulwich >=0.24.0 <1.2.8 (fixed))

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