Enterprise Server: Server-Side Request Forgery
CVE-2026-18730 is a high-severity server-side request forgery vulnerability in Enterprise Server from GitHub, with a CVSS 3.1 base score of 7.4 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 3.17.*, 3.18.*, 3.19.* as the first without the flaw, so updating Enterprise Server to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.48% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Enterprise Server to 3.17.* or 3.18.* or 3.19.* or 3.20.*, whichever matches your release line, or a later version.
- 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 |
|---|---|---|---|
| GitHub | Enterprise Server | 3.17.0 up to, but not including, 3.17.*; 3.18.0 up to, but not including, 3.18.*; 3.19.0 up to, but not including, 3.19.*; 3.20.0 up to, but not including, 3.20.*; 3.21.0 up to, but not including, 3.21.* | 3.17.*, 3.18.*, 3.19.*, 3.20.*, 3.21.* |
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
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.2 | High | CNA (github.com) |
| CVSS 3.1 | 7.4 | High | NVD |
Official description
A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to cause the Manage API to send crafted outbound requests to an attacker-controlled host. An unauthenticated endpoint parsed an attacker-supplied cluster configuration and issued gateway-to-agent requests whose HMAC authenticated only a timestamp, not the request path or body. An attacker positioned to intercept the outbound request could capture this token and replay it against privileged management agent endpoints. High-availability deployments were not affected due to a topology restriction. This vulnerability affected GitHub Enterprise Server releases in the 3.17, 3.18, 3.19, 3.20, and 3.21 series and was fixed in versions 3.17.21, 3.18.15, 3.19.12, 3.20.8, and 3.21.6. This vulnerability was reported via the GitHub Bug Bounty program.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Server-Side Request Forgery
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
How developers prevent this class of flaw
- If there is a known list of applications, IP, hostname, and/or domains to which the product is allowed to communicate, then use allowlists to ensure that outgoing requests are restricted to these known entities. The allowlists could be in the application code or possibly enforced by firewalls or network segmentation.
- If the product is expected to be able to connect to arbitrary IP addresses or domains, consider using a denylist that includes private network addresses, internal domain names, etc. The denylist could be in the application code or possibly enforced by firewalls or network segmentation.
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
- docs.github.com/en/[email protected]/admin/release-notes#3.17.21
- docs.github.com/en/[email protected]/admin/release-notes#3.18.15
- docs.github.com/en/[email protected]/admin/release-notes#3.19.12
- docs.github.com/en/[email protected]/admin/release-notes#3.20.8
- docs.github.com/en/[email protected]/admin/release-notes#3.21.6
Other vulnerabilities in Enterprise Server
- 7.7 High severity
- 8.8 High severity
- 9.8 Critical severity
- 8.8 High severity
- 7.5 High severity
- 7.5 High severity
Recent Server-Side Request Forgery vulnerabilities
- 8.3 High severity
- 7.7 High severity
- 7.7 High severity
- 7.3 High severity
- 8.6 High severity
- 8.5 High severity
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