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MEDIUM severity

GHSA-4p9g-qgx9-397p

MEDIUM

GHSA-4p9g-qgx9-397p is a medium-severity (CVSS 5.9) CWE-405 vulnerability in typo3/cms-core. O3 Security confirms whether GHSA-4p9g-qgx9-397p is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Denial of Service in Page Error Handling

Also known asBIT-typo3-2021-21359CVE-2021-21359
Published
Mar 23, 2021
Updated
Jul 8, 2026
Affected
6 pkgs
Patched
6 / 6
Exploits
None indexed
Exploitation data as of Jul 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

6 pkgs affected
🐘typo3/cms-core🐘typo3/cms-core🐘typo3/cms-core🐘typo3/cms🐘typo3/cms🐘typo3/cms

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Meta

  • CVSS: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:F/RL:O/RC:C (5.5)
  • CWE-405, CWE-674
  • Status: DRAFT

Problem

Requesting invalid or non-existing resources via HTTP triggers the page error handler which again could retrieve content to be shown as error message from another page. This leads to a scenario in which the application is calling itself recursively - amplifying the impact of the initial attack until the limits of the web server are exceeded.

Solution

Update to TYPO3 versions 9.5.25, 10.4.14, 11.1.1 that fix the problem described.

Credits

Thanks to Paul Keller, Mathias Bolt Lesniak and Kay Strobach who reported this issue and to TYPO3 framework merger Frank Nägler and to TYPO3 security team member Torben Hansen who fixed the issue.

References

Affected Packages

6 total 6 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagisttypo3/cms-core10.0.0&&< 10.4.1410.4.14
🐘Packagisttypo3/cms-core11.0.0&&< 11.1.111.1.1
🐘Packagisttypo3/cms-core9.0.0&&< 9.5.259.5.25
🐘Packagisttypo3/cms10.0.0&&< 10.4.1410.4.14
🐘Packagisttypo3/cms11.0.0&&< 11.1.111.1.1
🐘Packagisttypo3/cms9.0.0&&< 9.5.259.5.25

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for typo3/cms-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update typo3/cms-core to 10.4.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4p9g-qgx9-397p is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether GHSA-4p9g-qgx9-397p is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-4p9g-qgx9-397p. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

> ### Meta > * CVSS: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:F/RL:O/RC:C` (5.5) > * CWE-405, CWE-674 > * Status: **DRAFT** ### Problem Requesting invalid or non-existing resources via HTTP triggers the page error handler which again could retrieve content to be shown as error message from another page. This leads to a scenario in which the application is calling itself recursively - amplifying the impact of the initial attack until the limits of the web server are exceeded. ### Solution Update to TYPO3 versions 9.5.25, 10.4.14, 11.1.1 that fix the problem described. ### Credits Th
O3 Security · Impact-Aware SCA

Is GHSA-4p9g-qgx9-397p in your dependencies?

O3 detects GHSA-4p9g-qgx9-397p across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.