Vulnerability Report

CVE-2026-1999

Title: SSRF in GitHub Enterprise Server webhooks

Other

Proof Of Concept

PoC Available for CVE-2026-1999

CWE Category CWE-863

Published Date Feb 18, 2026

Modified Date Apr 08, 2026

Exploit Status Available

Score 7.1 CVSS v4.0

Exploit Probability (EPSS)

0.04%

Vulnerability Summary

CVE-2026-1999: An incorrect authorization vulnerability was identified in GitHub Enterprise Server that allowed an attacker to merge their own pull request into a repository without having push access by exploiting an authorization bypass in the enable_auto_merge mutation for pull requests. This issue only affected repositories that allow forking as the attack relies on opening a pull request from an attacker-controlled fork into the target repository. Exploitation was only possible in specific scenarios. It required a clean pull request status and only applied to branches without branch protection rules enabled. This vulnerability affected GitHub Enterprise Server versions prior to 3.19.2, 3.18.5, and 3.17.11, and was fixed in versions 3.19.2, 3.18.5, and 3.17.11. This vulnerability was reported via the GitHub Bug Bounty program.

Impacted Vendors

github 1

blackberry 1

Reference Links

https://docs.github.com/en/[email protected]/admin/release-notes#3.17.11 https://docs.github.com/en/[email protected]/admin/release-notes#3.18.5 https://docs.github.com/en/[email protected]/admin/release-notes#3.19.2

CVSS v4.0

Source Entity [email protected]

Severity HIGH

7.1

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

N/A

RAW VECTOR

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS v3.1

Source Entity [email protected]

Severity MEDIUM

6.5