CVE-2026-49400
LowCVSS 3.3Exploitation Probability (EPSS)
Low risk8th percentile - higher than 8% of all known CVEs
Summary
October CMS versions prior to 3.7.17 and 4.2.21 contain a PHP object injection vulnerability in the system module. The backend `SessionMaker` trait stored widget session state as `base64(serialize(...))` and consumed it with `unserialize()` without an `allowed_classes` restriction, allowing attacker-controlled bytes to trigger object injection and reachable PHP gadget chains. This issue only affects installations with `cms.safe_mode` enabled, which is an opt-in feature for demo or multi-tenant scenarios.
Risk Assessment
In environments with Safe Mode enabled, an attacker with access to the CMS markup editor could achieve remote code execution (RCE) via PHP object injection, leading to full system compromise. In standard deployments without Safe Mode, the risk is minimal, but updating is still recommended.
Recommendation
Update October CMS to version 3.7.17 or 4.2.21 immediately, as these versions patch the vulnerability. If updating is not possible, restrict markup editor access to fully trusted administrators only.
Other vulnerabilities in October CMS
See all- CVE-2017-16941High
October CMS through 1.0.428 does not prevent the use of .htaccess in themes, allowing remote authenticated users to execute arbitrary PHP code by downloading a theme ZIP archive from /backend/cms/themes, and then uploading and importing a modified archive with two new files: a .php file and a .htaccess file.
- CVE-2017-1000195High
October CMS version 412 is vulnerable to PHP object injection in asset move functionality, allowing for the deletion of files limited by file permissions on the server.
- CVE-2017-1000119High
October CMS version 412 is vulnerable to PHP code execution in the file upload functionality, potentially leading to site compromise and possibly affecting other applications on the server.
- CVE-2021-32648HighActively exploited
A vulnerability in the october/system package of October CMS allows an attacker to request an account password reset and then gain access to the account using a specially crafted request. The issue has been patched in Build 472 and v1.1.5.
- CVE-2017-1000197Critical
October CMS version 412 is vulnerable to file path modification in asset move functionality, potentially allowing the creation of malicious files on the server.
- CVE-2017-1000196Critical
October CMS version 412 is vulnerable to PHP code execution in the asset manager functionality, potentially leading to site compromise and possibly affecting other applications on the server.
- CVE-2017-1000194Critical
October CMS build 412 is vulnerable to Apache configuration modification via file upload functionality, potentially leading to site compromise and affecting other applications on the server.
- CVE-2026-46696Low
A vulnerability in the October CMS system module's Twig sandbox security policy allowed a chained bypass when cms.safe_mode is enabled. By combining unrestricted access to the Laravel session store with unblocked raw SQL methods reachable through Eloquent's __call forwarding, a backend user with CMS markup editing access could read arbitrary database values and write to the backend authentication session key, forging a session as another existing user. The issue is patched in versions 3.7.17 and 4.2.21.
- CVE-2026-25133Medium
October CMS versions prior to 3.7.14 and 4.1.10 contain a stored cross-site scripting vulnerability in the SVG sanitization logic. The regex pattern used to strip event handler attributes could be bypassed using a crafted payload, allowing malicious SVG files to be uploaded through the Media Manager with embedded JavaScript. Exploitation could lead to privilege escalation if a superuser views or embeds the malicious SVG, and requires authenticated backend access with media upload permissions.
- CVE-2026-25125Medium
October CMS before versions 3.7.14 and 4.1.10 contains a server-side information disclosure vulnerability in the INI settings parser. PHP's parse_ini_string() supports ${} syntax for environment variable interpolation, allowing attackers with Editor access to inject patterns like ${APP_KEY}, leading to exposure of sensitive environment variables.
Original NVD description (English source)
October System provides the system module for October Content Management System. Prior to versions 3.7.17 and 4.2.21, the backend `SessionMaker` trait stored widget session state as `base64(serialize(...))` and consumed it with `unserialize()` without an `allowed_classes` restriction. Any code path that could write to a `widget.*` session key with attacker-controlled bytes could trigger PHP object injection the next time the widget read its session state, allowing instantiation of arbitrary classes and reachable PHP gadget chains. This issue only affects installations running with `cms.safe_mode` enabled. Safe Mode is a niche opt-in feature, primarily used for demo installations and multi-tenant or shared-editor scenarios where untrusted users are deliberately granted access to the CMS markup editor. In standard production deployments Safe Mode is off, backend access is restricted to trusted administrators, and a markup editor can already execute arbitrary PHP directly. The session-write path that reaches this sink is gated by the Safe Mode sandbox, so installations without Safe Mode enabled are not exposed. Scope of impact is narrow even with Safe Mode enabled. The standard backend code paths that populate widget session state (search terms, sort options, selected IDs, filter values) wrap the input inside a known array shape before serializing, so user-supplied values never reach `unserialize()` as a controllable serialized payload. Exploitation requires the Safe Mode session-write path together with a suitable PHP gadget chain reachable from the installed dependency set. The hardening below removes the underlying object-injection sink so the class of issue is closed off regardless. The vulnerability has been patched in v3.7.17 and v4.2.21. Two changes were applied. `Backend\Traits\SessionMaker` now stores widget session state as plain JSON instead of `base64(serialize(...))`, eliminating the object-injection sink entirely for new writes. Reads transparently fall back to the legacy format for one upgrade cycle so existing sessions retain their saved widget state. The legacy `unserialize()` fallback path now sets `allowed_classes => false`, so even values written before the upgrade cannot instantiate objects. As a workaround, restrict CMS markup editing access to fully trusted administrators only, the standard October CMS recommendation for any deployment.