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GHSA-4h9c-v5vg-5m6m

HIGH

Access to restricted PHP code by dynamic static class access in smarty

Also known asCVE-2021-21408
Published
Jan 12, 2022
Updated
Mar 13, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed

EPSS Exploitation Probability

via FIRST.org ↗
2.2%probability of exploitation in next 30 days
Lower Risk80th percentile+1.75%
0.00%0.94%1.87%2.81%0.3%2.2%Dec 25Apr 26Jun 26

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.

Blast Radius

2 pkgs affected
🐘smarty/smarty🐘smarty/smarty

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

Impact

Template authors could run restricted static php methods.

Patches

Please upgrade to 3.1.40 or higher.

References

See the documentation on Smarty security features on the static_classes access filter.

For more information

If you have any questions or comments about this advisory please open an issue in the Smarty repo

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistsmarty/smartyall versions3.1.43
🐘Packagistsmarty/smarty4.0.0&&< 4.0.34.0.3

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for smarty/smarty. 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 smarty/smarty to 3.1.43 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4h9c-v5vg-5m6m 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-4h9c-v5vg-5m6m 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-4h9c-v5vg-5m6m. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Impact Template authors could run restricted static php methods. ### Patches Please upgrade to 3.1.40 or higher. ### References See the [documentation on Smarty security features](https://www.smarty.net/docs/en/advanced.features.tpl#advanced.features.security) on the static_classes access filter. ### For more information If you have any questions or comments about this advisory please open an issue in [the Smarty repo](https://github.com/smarty-php/smarty)
O3 Security · Impact-Aware SCA

Is GHSA-4h9c-v5vg-5m6m in your dependencies?

O3 detects GHSA-4h9c-v5vg-5m6m across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.