fief-server Server-Side Template Injection vulnerability

Exploitation

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

CVSS

10.0 · CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Server-Side Template Injection Overview of the Vulnerability Server-Side Template Injection (SSTI) is a vulnerability within application templating engines where user input is improperly handled and is embedded into the template, possibly leading code being executed. An attacker can use SSTI to execute code on the underlying system by manipulating values within the embedded template. When code is executed within the underlying system, it can allow an attacker to run permissioned commands under the exploited process, or exploit Cross-Site Scripting (XSS) to run code within the user's browser. Business Impact SSTI can lead to reputational damage for the business due to a loss in confidence and trust by users. If an attacker successfully executes code within the underlying system, it can result in data theft and indirect financial losses. Steps to Reproduce 1. Sign up and login to your account 1. Use a browser to navigate to: email-templates {{URL}} 1. put your payload in Edit Base…

Published by the source

23 Jun 2023, 21:46 UTC

Last modified by the source

2 Sep 2026, 22:15 UTC

Source last checked

26 Oct 2026, 13:51 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hj8m-9fhf-v7jp

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-hj8m-9fhf-v7jp

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# Patch Next advisory brief: GHSA-hj8m-9fhf-v7jp

Advisory: fief-server Server-Side Template Injection vulnerability
IDs: GHSA-hj8m-9fhf-v7jp
Record: https://patchnext.com/advisories/ghsa-hj8m-9fhf-v7jp (revision 2, source checked 26 Oct 2026, 13:51 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: fief-server 0.25.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI fief-server: affected >= 0.19.0, < 0.25.3; fixed in 0.25.3

## Suggested inspection (read-only)
- `python -m pip show fief-server`: 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 fief-server.
- 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-hj8m-9fhf-v7jp (OSV record GHSA-hj8m-9fhf-v7jp lists affected ranges: PyPI fief-server >=0.19.0 <0.25.3 (fixed))
- Verified: https://github.com/advisories/GHSA-hj8m-9fhf-v7jp (GitHub-reviewed advisory GHSA-hj8m-9fhf-v7jp lists affected ranges: PyPI fief-server >=0.19.0 <0.25.3)

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