CVE-2026-1999Network attack vector

Unauthorized pull request merge via faulty authorization

Published Feb 18, 2026 · Updated Feb 18, 2026

Incorrect authorization in GitHub Enterprise Server allows remote authenticated users to merge pull requests without push access. The enable_auto_merge GraphQL mutation accepts a pull request from an attacker-controlled fork without correctly enforcing the target repository's push authorization. The repository must allow forks, the pull request must have a clean status, and the target branch must lack branch protection, enabling unauthorized source changes.

CVSS severity7.1
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in GitHub Enterprise Server allows remote authenticated users to merge pull requests without push access. The enable_auto_merge GraphQL mutation accepts a pull request from an attacker-controlled fork without correctly enforcing the target repository's push authorization. The repository must allow forks, the pull request must have a clean status, and the target branch must lack branch protection, enabling unauthorized source changes.

The record

CVE
CVE-2026-1999
Published
Feb 18, 2026
Updated
Feb 18, 2026
Vendor
Twitter
Product
GitHub Enterprise Server
Classifications
CWE-863, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.17.0 <3.17.11 changes=[{"at":"3.17.11","status":"unaffected"}]
  2. Affected versionversion=3.18.0 <3.18.5 changes=[{"at":"3.18.5","status":"unaffected"}]
  3. Affected versionversion=3.19.0 <3.19.2 changes=[{"at":"3.19.2","status":"unaffected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Twitter · GitHub Enterprise Serverversion=3.17.0 <3.17.11 changes=[{"at":"3.17.11","status":"unaffected"}]; version=3.18.0 <3.18.5 changes=[{"at":"3.18.5","status":"unaffected"}]; version=3.19.0 <3.19.2 changes=[{"at":"3.19.2","status":"unaffected"}]

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
7.1GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:L/SC:L/SI:H/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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