How severe is CVE-2026-39850?

CVE-2026-39850 has a CVSS score of 7.4/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-39850?

CVE-2026-39850 affects the following packages: yiisoft/yii2 (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-39850?

Update yiisoft/yii2 to 2.0.55 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39850 is resolved across your whole dependency graph.

How do I detect CVE-2026-39850 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yiisoft/yii2. 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.

How do I mitigate CVE-2026-39850 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2026-39850?

O3 pinpoints whether CVE-2026-39850 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2026-39850 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-39850 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was CVE-2026-39850 published, and has it been updated?

CVE-2026-39850 was published on May 20, 2026 and was last updated on August 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

HIGH severity

CVE-2026-39850

HIGHFix: yiisoft/yii2@109878b

CVE-2026-39850 is a high-severity (CVSS 7.4) remote code execution vulnerability in yiisoft/yii2. O3 Security confirms whether CVE-2026-39850 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Yii 2: Local file inclusion via view parameter name collision

Also known asGHSA-5vpg-rj7q-qpw2

Published

May 20, 2026

Updated

Aug 7, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Aug 7, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🐘yiisoft/yii2

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

Yii 2 is a PHP application framework. Versions 2.0.54 and prior contain flawed logic in the core view rendering method View::renderPhpFile() that leads to Local File Inclusion. The function calls extract($params, EXTR_OVERWRITE) before the require statement that loads the view file. As a result, a caller-controlled file key in the $params array overwrites the internal local variable specifying which file to include, potentially enabling RCE if an attacker can write PHP files through a separate primitive, as well as information disclosure. This issue has been fixed in version 2.0.55.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`yiisoft/yii2`	all versions	2.0.55

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yiisoft/yii2. 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 yiisoft/yii2 to 2.0.55 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39850 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-2026-39850 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-2026-39850. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

Yii 2 is a PHP application framework. Versions 2.0.54 and prior contain flawed logic in the core view rendering method View::renderPhpFile() that leads to Local File Inclusion. The function calls extract($_params_, EXTR_OVERWRITE) before the require statement that loads the view file. As a result, a caller-controlled _file_ key in the $params array overwrites the internal local variable specifying which file to include, potentially enabling RCE if an attacker can write PHP files through a separate primitive, as well as information disclosure. This issue has been fixed in version 2.0.55.

O3 Security · Impact-Aware SCA

Is CVE-2026-39850 in your dependencies?

O3 detects CVE-2026-39850 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works