GHSA-4j38-f5cw-54h7
GHSA-4j38-f5cw-54h7 is a CWE-116 vulnerability in twig/twig. O3 Security confirms whether GHSA-4j38-f5cw-54h7 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Twig: The `spaceless` filter implicitly marks its output as safe
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for GHSA-4j38-f5cw-54h7.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
twig/twigReal-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
Description
The spaceless filter is registered with is_safe => ['html'], which means Twig's autoescaper does not escape its output in an HTML context. As a result, applying spaceless to attacker-controlled input that contains markup emits the markup unescaped even when the developer never wrote |raw and autoescape is enabled.
Example:
{% set payload = '<script>alert()</script>' %}
{{ payload }} {# escaped #}
{{ payload|spaceless }} {# not escaped #}
The filter is deprecated but still functional. With the deprecation, some downstream projects (e.g. Drupal modules) have duplicated the filter and inherited the same is_safe flag.
Resolution
The spaceless filter no longer marks its output as safe. Documentation has been updated to warn that spaceless should not be applied to unsanitised user input.
Credits
Twig would like to thank Pierre Rudloff for reporting the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | twig/twig | all versions | 3.26.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for twig/twig. 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.
Fix
Update twig/twig to 3.26.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4j38-f5cw-54h7 is resolved across your whole dependency graph.
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.
How O3 protects you
O3 pinpoints whether GHSA-4j38-f5cw-54h7 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-4j38-f5cw-54h7. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-4j38-f5cw-54h7 in your dependencies?
O3 detects GHSA-4j38-f5cw-54h7 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.