Jinja2 sandbox escape via string formatting

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2019-10906: 3.53% estimated exploitation activity in the next 30 days; percentile 89.28 (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.

In Pallets Jinja before 2.10.1, str.formatmap allows a sandbox escape. The sandbox is used to restrict what code can be evaluated when rendering untrusted, user-provided templates. Due to the way string formatting works in Python, the str.formatmap method could be used to escape the sandbox. This issue was previously addressed for the str.format method in Jinja 2.8.1, which discusses the issue in detail. However, the less-common str.formatmap method was overlooked. This release applies the same sandboxing to both methods. If you cannot upgrade Jinja, you can override the issafeattribute method on the sandbox and explicitly disallow the formatmap method on string objects.

Published by the source

10 Apr 2019, 14:30 UTC

Last modified by the source

24 Sep 2024, 21:03 UTC

Source last checked

26 Oct 2026, 13:18 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-462w-v97r-4m45

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-462w-v97r-4m45

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# Patch Next advisory brief: CVE-2019-10906

Advisory: Jinja2 sandbox escape via string formatting
IDs: CVE-2019-10906, GHSA-462w-v97r-4m45
Record: https://patchnext.com/advisories/cve-2019-10906 (revision 3, source checked 26 Oct 2026, 13:18 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: jinja2 2.10.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI jinja2: affected < 2.10.1; fixed in 2.10.1

## Suggested inspection (read-only)
- `python -m pip show jinja2`: 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 jinja2.
- 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-462w-v97r-4m45 (OSV record GHSA-462w-v97r-4m45 lists affected ranges: PyPI jinja2 >=0 <2.10.1 (fixed))
- Verified: https://github.com/advisories/GHSA-462w-v97r-4m45 (GitHub-reviewed advisory GHSA-462w-v97r-4m45 lists affected ranges: PyPI jinja2 >=0 <2.10.1)

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