PickleScan's pkgutil.resolve_name has a universal blocklist bypass

Exploitation

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

CVSS

10.0 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS

• CVE-2026-3490: 0.82% estimated exploitation activity in the next 30 days; percentile 57.38 (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.

Summary pkgutil.resolvename() is a Python stdlib function that resolves any "module:attribute" string to the corresponding Python object at runtime. By using pkgutil.resolvename as the first REDUCE call in a pickle, an attacker can obtain a reference to ANY blocked function (e.g., os.system, builtins.exec, subprocess.call) without that function appearing in the pickle's opcodes. picklescan only sees pkgutil.resolvename (which is not blocked) and misses the actual dangerous function entirely. This defeats picklescan's entire blocklist concept — every single entry in unsafeglobals can be bypassed. Severity Critical (CVSS 10.0) — Universal bypass of all blocklist entries. Any blocked function can be invoked. Affected Versions - picklescan <= 1.0.3 (all versions including latest) Details How It Works A pickle file uses two chained REDUCE calls: picklescan's opcode scanner sees: - STACKGLOBAL with module=pkgutil, name=resolvename → NOT in blocklist → CLEAN - The second REDUCE operates on…

Published by the source

3 Mar 2026, 20:04 UTC

Last modified by the source

29 Jun 2026, 12:26 UTC

Source last checked

26 Oct 2026, 13:45 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vvpj-8cmc-gx39

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-vvpj-8cmc-gx39

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-vvpj-8cmc-gx39

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# Patch Next advisory brief: CVE-2026-3490

Advisory: PickleScan's pkgutil.resolve_name has a universal blocklist bypass
IDs: CVE-2026-3490, GHSA-vvpj-8cmc-gx39
Record: https://patchnext.com/advisories/cve-2026-3490 (revision 3, source checked 26 Oct 2026, 13:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 10.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: picklescan 1.0.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI picklescan: affected < 1.0.4; fixed in 1.0.4

## Suggested inspection (read-only)
- `python -m pip show picklescan`: 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 picklescan.
- 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-vvpj-8cmc-gx39 (GitHub-reviewed advisory GHSA-vvpj-8cmc-gx39 lists affected ranges: PyPI picklescan >=0 <1.0.4)
- Verified: https://osv.dev/vulnerability/GHSA-vvpj-8cmc-gx39 (OSV record GHSA-vvpj-8cmc-gx39 lists affected ranges: PyPI picklescan >=0 <1.0.4 (fixed))

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