Summary
The core view rendering method View::renderPhpFile() calls extract($_params_, EXTR_OVERWRITE) before the require statement that includes the view file. A caller-controlled parameter named _file_ in the $params array overwrites the internal local variable that specifies which file is included, enabling a Local File Inclusion primitive.
Workarounds
No.
Impact
- Local File Inclusion (arbitrary file read via non-PHP files)
- Potential RCE if attacker can write PHP files via a separate primitive
- Information disclosure
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
CVE-2026-39850 has a CVSS score of 7.4 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.0.55); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
2.0.55
Frequently Asked Questions
- What is CVE-2026-39850? CVE-2026-39850 is a high-severity improper input validation vulnerability in yiisoft/yii2 (composer), affecting versions < 2.0.55. It is fixed in 2.0.55. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- How severe is CVE-2026-39850? CVE-2026-39850 has a CVSS score of 7.4 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of yiisoft/yii2 are affected by CVE-2026-39850? yiisoft/yii2 (composer) versions < 2.0.55 is affected.
- Is there a fix for CVE-2026-39850? Yes. CVE-2026-39850 is fixed in 2.0.55. Upgrade to this version or later.
- Is CVE-2026-39850 exploitable, and should I be worried? Whether CVE-2026-39850 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-39850 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-39850? Upgrade
yiisoft/yii2to 2.0.55 or later.