Path traversal in impacket

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

9.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2021-31800: 19.41% estimated exploitation activity in the next 30 days; percentile 97.36 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Multiple path traversal vulnerabilities exist in smbserver.py in Impacket before 0.9.23. An attacker that connects to a running smbserver instance can list and write to arbitrary files via ../ directory traversal. This could potentially be abused to achieve arbitrary code execution by replacing /etc/shadow or an SSH authorized key.

Published by the source

18 Jun 2021, 18:43 UTC

Last modified by the source

13 Feb 2025, 05:31 UTC

Source last checked

26 Oct 2026, 13:17 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-mj63-64x7-57xf

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-mj63-64x7-57xf

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# Patch Next advisory brief: CVE-2021-31800

Advisory: Path traversal in impacket
IDs: CVE-2021-31800, GHSA-mj63-64x7-57xf
Record: https://patchnext.com/advisories/cve-2021-31800 (revision 3, source checked 26 Oct 2026, 13:17 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: impacket 0.9.23. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI impacket: affected < 0.9.23; fixed in 0.9.23

## Suggested inspection (read-only)
- `python -m pip show impacket`: 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 impacket.
- 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://osv.dev/vulnerability/GHSA-mj63-64x7-57xf (OSV record GHSA-mj63-64x7-57xf lists affected ranges: PyPI impacket >=0 <0.9.23 (fixed))
- Verified: https://github.com/advisories/GHSA-mj63-64x7-57xf (GitHub-reviewed advisory GHSA-mj63-64x7-57xf lists affected ranges: PyPI impacket >=0 <0.9.23)

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