CVE-2026-24907: October/system Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-j4j5-9x6g-rgxc
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CVSS 5.4
CWE-79
Published
Advisory Summary

CVE-2026-24907 is a MODERATE (CVSS 5.4) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting October/system libraries in the Packagist ecosystem. The issue involves october cms has stored xss in event log mail preview. Remediation is available by upgrading affected packages to version 4.1.10, 3.7.14.

CVE-2026-24907 at a Glance

CVE Identifier CVE-2026-24907
GHSA Identifier GHSA-j4j5-9x6g-rgxc
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product October/system
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 5.4

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-24907

To remediate this vulnerability, upgrade all affected October/system dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

october/system fixed: 4.1.10 
Upgrade october/system to 4.1.10
october/system fixed: 3.7.14 
Upgrade october/system to 3.7.14
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for october/system

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-24907, inspect your project dependencies for October/system:

inspect dependencies for october/system

Analyze the terminal output to locate any version of October/system in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.1.10), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In October/system, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A stored cross-site scripting (XSS) vulnerability was identified in the Event Log mail preview feature. When viewing logged mail messages, HTML content was rendered in an iframe without proper sandboxing, allowing JavaScript execution in the viewer's browser context. ### Impact - Stored XSS via mail template content rendered in Event Log - Could allow privilege escalation if a superuser views a malicious log entry - Requires authenticated backend access with mail template editing permissions - Requires a superuser to view the specific Event Log entry to trigger ### Patches The vulnerability has been patched in v3.7.14 and v4.1.10. All users are encouraged to upgrade to the latest patched version. ### Workarounds If upgrading immediately is not possible: - Restrict mail template editing permissions to fully trusted administrators only - Restrict Event Log viewing permissions to minimize exposure ### References - Reported by [Chris Alupului](https://github.com/neosprings)

CVE-2026-24907 Affected October/system Versions

2 component(s)
Fixed Versions:
4.1.103.7.14
Product / Package Ecosystem Affected Versions Fixed Version
october/system
 Packagist
≥ 4.0.0
< 4.1.10
4.1.10
october/system
 Packagist
< 3.7.14
3.7.14

References

GitHub Advisory / Wiki ADVISORY
https://github.com/octobercms/october/security/advisories/GHSA-j4j5-9x6g-rgxc
NVD — CVE-2026-24907 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-24907
October/system Source Repository REPOSITORY
https://github.com/octobercms/october

Frequently Asked Questions

What is CVE-2026-24907?
CVE-2026-24907 is a security vulnerability in October/system involving October CMS has Stored XSS in Event Log Mail Preview under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which October/system versions are affected?
Affected versions include releases prior to 4.1.10, 3.7.14 across affected packages: october/system.
What version fixes CVE-2026-24907?
Upgrading to 4.1.10, 3.7.14 (or the latest patched release for your respective branch) resolves the vulnerability.
Is october/system affected?
Yes, october/system is affected in releases prior to 4.1.10, 3.7.14. Upgrade your dependency to 4.1.10, 3.7.14 or later.
What is the CVSS score of CVE-2026-24907?
CVE-2026-24907 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2026-24907?
CVE-2026-24907 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check Packagist dependencies for CVE-2026-24907?
Run the dependency tree command: 'inspect dependencies for october/system'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-j4j5-9x6g-rgxc",
  "modified" : "2026-04-24T21:06:19Z",
  "published" : "2026-04-14T20:02:50Z",
  "aliases" : [ "CVE-2026-24907" ],
  "summary" : "October CMS has Stored XSS in Event Log Mail Preview",
  "details" : "A stored cross-site scripting (XSS) vulnerability was identified in the Event Log mail preview feature. When viewing logged mail messages, HTML content was rendered in an iframe without proper sandboxing, allowing JavaScript execution in the viewer's browser context.\n\n### Impact\n- Stored XSS via mail template content rendered in Event Log\n- Could allow privilege escalation if a superuser views a malicious log entry\n- Requires authenticated backend access with mail template editing permissions\n- Requires a superuser to view the specific Event Log entry to trigger\n\n### Patches\nThe vulnerability has been patched in v3.7.14 and v4.1.10. All users are encouraged to upgrade to the latest patched version.\n\n### Workarounds\nIf upgrading immediately is not possible:\n- Restrict mail template editing permissions to fully trusted administrators only\n- Restrict Event Log viewing permissions to minimize exposure\n\n### References\n- Reported by [Chris Alupului](https://github.com/neosprings)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "october/system"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.1.10"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.1.9"
    }
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "october/system"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.7.14"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.7.13"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/octobercms/october/security/advisories/GHSA-j4j5-9x6g-rgxc"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-24907"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/octobercms/october"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-14T20:02:50Z",
    "nvd_published_at" : "2026-04-14T18:16:45Z"
  }
}