CVE-2026-103620
Missing authorization in GitHub Enterprise Server allowed repository writers to replace default branches via GraphQL
Description
A missing authorization vulnerability was identified in GitHub Enterprise Server that allowed a repository collaborator with write access to delete the current default branch through the GraphQL API and cause an attacker-controlled branch to become the new default. In repositories that required pull-request review but did not restrict branch deletion, this bypassed the review requirement and caused fresh clones and default-branch API requests to use attacker-controlled content. This vulnerability affected supported GitHub Enterprise Server releases in the 3.18, 3.19, 3.20, 3.21, and 3.22 series and was fixed in versions 3.18.16, 3.19.13, 3.20.9, 3.21.7, and 3.22.2. This vulnerability was reported via the GitHub Bug Bounty program.
INFO
Published Date :
Oct. 6, 2026, 7:17 p.m.
Last Modified :
Oct. 7, 2026, 5:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | MEDIUM | 82327ea3-741d-41e4-88f8-2cf9e791e760 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update GitHub Enterprise Server to version 3.18.16 or later.
- Update GitHub Enterprise Server to version 3.19.13 or later.
- Update GitHub Enterprise Server to version 3.20.9 or later.
- Update GitHub Enterprise Server to version 3.21.7 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-103620.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-103620 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-103620
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-103620 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-103620 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Oct. 07, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-103620', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-10-07T16:31:48.617666Z'} -
New CVE Received by [email protected]
Oct. 06, 2026
Action Type Old Value New Value Added Description A missing authorization vulnerability was identified in GitHub Enterprise Server that allowed a repository collaborator with write access to delete the current default branch through the GraphQL API and cause an attacker-controlled branch to become the new default. In repositories that required pull-request review but did not restrict branch deletion, this bypassed the review requirement and caused fresh clones and default-branch API requests to use attacker-controlled content. This vulnerability affected supported GitHub Enterprise Server releases in the 3.18, 3.19, 3.20, 3.21, and 3.22 series and was fixed in versions 3.18.16, 3.19.13, 3.20.9, 3.21.7, and 3.22.2. This vulnerability was reported via the GitHub Bug Bounty program. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/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 Added CWE CWE-862 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/103xxx/CVE-2026-103620.json">CVE-2026-103620</a> Added Reference https://docs.github.com/en/[email protected]/admin/release-notes#3.18.16 Added Reference https://docs.github.com/en/[email protected]/admin/release-notes#3.19.13 Added Reference https://docs.github.com/en/[email protected]/admin/release-notes#3.20.9 Added Reference https://docs.github.com/en/[email protected]/admin/release-notes#3.21.7 Added Reference https://docs.github.com/en/[email protected]/admin/release-notes#3.22.2