What’s Vulnerable › Vulnerabilities

CVE-2025-35939: Craft CMS External Control of Assumed-Immutable Web Parameter Vulnerability

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2025-06-02
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-05-07 · updated 2026-06-17
• Weakness: CWE-472

Description

Craft CMS stores arbitrary content provided by unauthenticated users in session files. This content could be accessed and executed, possibly using an independent vulnerability. Craft CMS redirects requests that require authentication to the login page and generates a session file on the server at '/var/lib/php/sessions'. Such session files are named 'sess_[session_value]', where '[session_value]' is provided to the client in a 'Set-Cookie' response header. Craft CMS stores the return URL requested by the client without sanitizing parameters. Consequently, an unauthenticated client can introduce arbitrary values, such as PHP code, to a known local file location on the server. Craft CMS versions 5.7.5 and 4.15.3 have been released to address this issue.

Affected products

• craftcms cms: before 4.15.3; from 5.0.0 before 5.7.5 — fixed in 4.15.3, 5.7.5

How to fix

Upgrade to a fixed version: craftcms cms 4.15.3, 5.7.5. Check the vendor advisory for mitigations.

References

• https://github.com/craftcms/cms/pull/17220
• https://github.com/craftcms/cms/releases/tag/4.15.3
• https://github.com/craftcms/cms/releases/tag/5.7.5
• https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/IT/white/2025/va-25-147-01.json
• https://www.cve.org/CVERecord?id=CVE-2025-35939
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-35939

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