matrix-hookshot: Improper Neutralization of Special Elements in Output Used by a Downstream Component
CVE-2023-43656 is a critical-severity improper neutralization of special elements in output used by a downstream component vulnerability in matrix-hookshot from Matrix-org, with a CVSS 3.1 base score of 9.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected matrix-hookshot versions: < 4.5.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.32% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Hookshot to 4.5.0 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Matrix-org | matrix-hookshot | < 4.5.0 | Not stated |
| Matrix | Hookshot | before 4.5.0 | 4.5.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 5.6 | Medium | CNA (github.com) |
| CVSS 3.1 | 9.0 | Critical | NVD |
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements in Output Used by a Downstream Component
The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.
How developers prevent this class of flaw
- Programming languages and supporting technologies might be chosen which are not subject to these issues.
- Utilize an appropriate mix of allowlist and denylist parsing to filter control-plane syntax from all input.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Improper Neutralization of Special Elements in Output Used by a Downstream Component vulnerabilities
- 7.8 High severity
- 10.0 Critical severity
- 7.7 High severity
- 9.8 Critical severity
- 8.2 High severity
- 7.2 High severity
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