CVE-2023-43656 [Medium] | Security Vulnerability in Hookshot

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.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-11-21	0.44%	0.30%	-0.15%
2	2025-11-18	0.30%	0.44%	+0.15%
3	2025-04-15	—	0.30%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-11-21

0.44%

0.30%

-0.15%

2025-11-18

0.30%

0.44%

+0.15%

2025-04-15

—

0.30%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.6	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:L` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:H) Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. 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:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	1.4	3.7	[email protected]
9.0	3.1	CRITICAL	`CVSS:3.1/AV:N/AC:H/PR:N/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:H) Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. 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.	2.2	6.0	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.6

3.1

MEDIUM

CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:L Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H): Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
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:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

1.4

3.7

[email protected]

9.0

3.1

CRITICAL

CVSS:3.1/AV:N/AC:H/PR:N/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:H): Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
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.

2.2

6.0

[email protected]

Affected software / configurations for CVE-2023-43656

Vendor	Product	Version	Raw CPE
matrix	hookshot	< 4.5.0	cpe:2.3:a:matrix:hookshot::::::::

References for CVE-2023-43656

URL	Tags
https://github.com/matrix-org/matrix-hookshot/commit/dc126afa6af86d66aefcd23a825326f405bcc894	Patch
https://github.com/matrix-org/matrix-hookshot/security/advisories/GHSA-fr97-pv6w-4cj6	Vendor Advisory

URL

CVE-2023-43656 | Sandbox escape for instances that have enabled transformation functions in matrix-hookshot

Exploit prediction scoring system (EPSS) score for CVE-2023-43656

Common vulnerability scoring system (CVSS) metrics for CVE-2023-43656

Weakness enumeration for CVE-2023-43656

Affected software / configurations for CVE-2023-43656

References for CVE-2023-43656