banks has Critical Remote Code Execution (RCE) via Jinja2 SSTI

Exploitation

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

CVSS

7.5 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-44209: 0.42% estimated exploitation activity in the next 30 days; percentile 36.68 (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 banks <= 2.4.1 uses jinja2.Environment() (unsandboxed) to render prompt templates. Applications that pass user-supplied strings as the template argument to Prompt() are vulnerable to Server-Side Template Injection (SSTI), which can lead to Remote Code Execution (RCE) on the host system. This is a vulnerability in how banks initializes its Jinja2 environment — not in Jinja2 itself. Vulnerable Code src/banks/env.py — the global Jinja2 environment is created without sandboxing: Attack Scenario An application that stores prompt templates in a database, accepts them via an API, or loads them from a user-supplied config file and passes them to Prompt() is vulnerable. For example: Proof of Concept Setup: PoC script: Confirmed output: python from banks import Prompt p = Prompt("{{ self.init.globals.builtins.import('os').popen('echo POC /tmp/rcebanksexec').read() }}") p.text() bash ls -l /tmp/rcebanksexec -rw-rw-r-- 1 ak ak 4 Apr 27 15:36 /tmp/rcebanksexec Impact Applications that…

Published by the source

8 May 2026, 20:36 UTC

Last modified by the source

13 Jul 2026, 16:42 UTC

Source last checked

26 Oct 2026, 13:45 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-gphh-9q3h-jgpp

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-gphh-9q3h-jgpp

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# Patch Next advisory brief: CVE-2026-44209

Advisory: banks has Critical Remote Code Execution (RCE) via Jinja2 SSTI
IDs: CVE-2026-44209, GHSA-gphh-9q3h-jgpp
Record: https://patchnext.com/advisories/cve-2026-44209 (revision 2, 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: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: banks 2.4.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI banks: affected <= 2.4.1; fixed in 2.4.2

## Suggested inspection (read-only)
- `python -m pip show banks`: 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 banks.
- 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-gphh-9q3h-jgpp (OSV record GHSA-gphh-9q3h-jgpp lists affected ranges: PyPI banks >=0 <2.4.2 (fixed))
- Verified: https://github.com/advisories/GHSA-gphh-9q3h-jgpp (GitHub-reviewed advisory GHSA-gphh-9q3h-jgpp lists affected ranges: PyPI banks >=0 <=2.4.1)

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