CVE-2026-103620 (GCVE-0-2026-103620)
Vulnerability from cvelistv5 – Published: 2026-10-06 18:56 – Updated: 2026-10-07 16:32
VLAI
EPSS
VEX
Title
Missing authorization in GitHub Enterprise Server allowed repository writers to replace default branches via GraphQL
Summary
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.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-07 16:31 UTC
CWE
- CWE-862 - Missing Authorization
Assigner
References
5 references
| URL | Tags |
|---|---|
| https://docs.github.com/en/enterprise-server@3.18… | release-notes |
| https://docs.github.com/en/enterprise-server@3.19… | release-notes |
| https://docs.github.com/en/enterprise-server@3.20… | release-notes |
| https://docs.github.com/en/enterprise-server@3.21… | release-notes |
| https://docs.github.com/en/enterprise-server@3.22… | release-notes |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| GitHub | Enterprise Server |
Affected:
3.18.0 , < 3.18.*
(semver)
Affected: 3.19.0 , < 3.19.* (semver) Affected: 3.20.0 , < 3.20.* (semver) Affected: 3.21.0 , < 3.21.* (semver) Affected: 3.22.0 , < 3.22.* (semver) |
guessed |
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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