October CMS safe mode bypass using Twig sandbox escape

Description

Impact

An authenticated backend user with the editor.cms_pages, editor.cms_layouts, or editor.cms_partials permissions who would normally not be permitted to provide PHP code to be executed by the CMS due to cms.safe_mode being enabled can write specific Twig code to escape the Twig sandbox and execute arbitrary PHP.

This is not a problem for anyone who trusts their users with those permissions to usually write and manage PHP within the CMS by not having cms.safe_mode enabled. Still, it would be a problem for anyone relying on cms.safe_mode to ensure that users with those permissions in production do not have access to write and execute arbitrary PHP.

Patches

This issue has been patched in v3.4.15.

Workarounds

As a workaround, remove the specified permissions from untrusted users.

References

Credits to:
- Vasiliy Bodrov

For more information

If you have any questions or comments about this advisory:
* Email us at [email protected]

Basic information

Type
reviewed
Severity
critical
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2023-11-29 21:33:21 UTC
Updated
2023-12-04 15:18:39 UTC
GitHub reviewed
2023-11-29 21:33:21 UTC
NVD published
2023-12-01

EPSS Score

Score Percentile
0.25% 47.74%

CVSS Scores

Base score Version Severity Vector
9.1 3.1
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.

Identifiers

CWEs

CWE id Name
CWE-94 Improper Control of Generation of Code ('Code Injection')

Credits

  • whatev3n (analyst)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
composer october/system >= 3.0.0, < 3.4.15 3.4.15

References

cvelogic Threat Intelligence