CVE-2023-43656: matrix-hookshot is a Matrix bot for connecting to external services like GitHub, GitLab, JIRA, and more. Instances that have enabled transformation fu...

Description

matrix-hookshot is a Matrix bot for connecting to external services like GitHub, GitLab, JIRA, and more. Instances that have enabled transformation functions (those that have `generic.allowJsTransformationFunctions` in their config), may be vulnerable to an attack where it is possible to break out of the `vm2` sandbox and as a result Hookshot will be vulnerable to this. This problem is only likely to affect users who have allowed untrusted users to apply their own transformation functions. If you have only enabled a limited set of trusted users, this threat is reduced (though not eliminated). Version 4.5.0 and above of hookshot include a new sandbox library which should better protect users. Users are advised to upgrade. Users unable to upgrade should disable `generic.allowJsTransformationFunctions` in the config.

Metrics

CVSS 3.1

9/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

0.28%

20.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-74

Affected Software

Vendor	Product	Versions
Matrix	Hookshot	< 4.5.0

References

Timeline

Published: Sep 27, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-43656?

matrix-hookshot is a Matrix bot for connecting to external services like GitHub, GitLab, JIRA, and more. Instances that have enabled transformation functions (those that have `generic.allowJsTransformationFunctions` in their config), may be vulnerable to an attack where it is possible to break out of the `vm2` sandbox and as a result Hookshot will be vulnerable to this. This problem is only likely to affect users who have allowed untrusted users to apply their own transformation functions. If you have only enabled a limited set of trusted users, this threat is reduced (though not eliminated). Version 4.5.0 and above of hookshot include a new sandbox library which should better protect users. Users are advised to upgrade. Users unable to upgrade should disable `generic.allowJsTransformationFunctions` in the config.

How severe is CVE-2023-43656?

CVE-2023-43656 has a CVSS score of 9/10 (CRITICAL severity). The EPSS model estimates a 0.28% probability of exploitation in the next 30 days.

How do I fix CVE-2023-43656?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.