Enterprise Server: Time-of-check Time-of-use (TOCTOU) Race Condition
CVE-2026-19118 is a high-severity time-of-check time-of-use (TOCTOU) race condition vulnerability in Enterprise Server from GitHub, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected Enterprise Server versions: 3.17.0 through 3.17.19; 3.18.0 through 3.18.13; 3.19.0 through 3.19.10, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.91% chance of exploitation within 30 days, higher than 61% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Enterprise Server you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on docs.github.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| GitHub | Enterprise Server | 3.17.0 through 3.17.19; 3.18.0 through 3.18.13; 3.19.0 through 3.19.10; 3.20.0 through 3.20.6; 3.21.0 through 3.21.4 | Not stated |
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
- LowA basic user account is enough.
- 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
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 7.7 | High | CNA (github.com) |
| CVSS 3.1 | 7.5 | High | NVD |
Official description
A time-of-check time-of-use race condition vulnerability was identified in GitHub Enterprise Server that allowed remote code execution. Exploitation required an authenticated user with write access to a repository and precise timing of concurrent upload requests. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.17.20, 3.18.14, 3.19.11, 3.20.7, and 3.21.5. 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: Time-of-check Time-of-use (TOCTOU) Race Condition
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
How developers prevent this class of flaw
- The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
- When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.
- Limit the interleaving of operations on files from multiple processes.
More Time-of-check Time-of-use (TOCTOU) Race Condition vulnerabilities (CWE-367)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- docs.github.com/en/[email protected]/admin/release-notes#3.17.20Release Notes
- docs.github.com/en/[email protected]/admin/release-notes#3.18.14Release Notes
- docs.github.com/en/[email protected]/admin/release-notes#3.19.11Release Notes
- docs.github.com/en/[email protected]/admin/release-notes#3.20.7Release Notes
- docs.github.com/en/[email protected]/admin/release-notes#3.21.5Release Notes
Other vulnerabilities in Enterprise Server
- 7.7 High severity
- 8.8 High severity
- 9.8 Critical severity
- 8.8 High severity
- 7.4 High severity
- 7.5 High severity
Recent Time-of-check Time-of-use (TOCTOU) Race Condition vulnerabilities
- 9.3 Critical severity
- 7.3 High severity
- 8.1 High severity
- 7.8 High severity
- 8.1 High severity
- 8.1 High severity
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