CVE-2021-26120
CRITICALCVE-2021-26120 is a critical-severity (CVSS 9.8) Code Injection vulnerability in smarty/smarty. O3 Security confirms whether CVE-2021-26120 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
PHP Code Injection by malicious function name in smarty
Real-World Exposure
smarty/smartyReal-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
Smarty before 3.1.39 allows code injection via an unexpected function name after a {function name= substring.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | smarty/smarty | all versions | 3.1.39 |
Detection & mitigation playbook
Open-source dependencyDetect
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.
Fix
Update smarty/smarty to 3.1.39 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-26120 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 CVE-2021-26120 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 CVE-2021-26120. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Frequently Asked Questions
Is CVE-2021-26120 in your dependencies?
O3 detects CVE-2021-26120 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.