CVE-2026-103620: A missing authorization vulnerability was identified in GitHub Enterprise Server that allowed a repository col

Routine

MEDIUM 6.5UPGRADE

CVE-2026-103620 is a medium-severity flaw (CVSS 6.5) affecting enterprise server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.5% (top 57%)
CISA exploited list	No
Weakness	CWE-862
Published	2026-10-06
Last modified	2026-10-20

Publisher (CNA): GitHub, Inc. (Products Only) · Vendor: github

Last updated 2026-10-20 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-10-06 19:17 UTCPublished CVE record published
2026-10-20 19:33 UTCUpdated Record last modified

github enterprise server UPGRADE

Affected: >= 3.18.0 and < 3.18.16 · >= 3.19.0 and < 3.19.13 · >= 3.20.0 and < 3.20.9 · >= 3.21.0 and < 3.21.7 · >= 3.22.0 and < 3.22.2

Fixed in: 3.18.16, 3.19.13, 3.20.9, 3.21.7, 3.22.2

Safe to downgrade to: a release before 3.18.0

1. Check installed version

apt-cache policy enterprise-server || rpm -q enterprise-server || enterprise-server --version

2. UPGRADE to 3.18.16 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade enterprise-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade enterprise-server

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.18.0 (Debian / Ubuntu)

apt-cache madison enterprise-server sudo apt install enterprise-server=<VERSION_BEFORE_3.18.0> sudo apt-mark hold enterprise-server

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list enterprise-server sudo dnf downgrade enterprise-server-<VERSION_BEFORE_3.18.0> sudo dnf versionlock add enterprise-server

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-103620?

enterprise server: upgrade to 3.18.16, 3.19.13, 3.20.9, 3.21.7, 3.22.2. Exact commands for each OS are on this page.

Is CVE-2026-103620 being exploited?

CVE-2026-103620 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-103620 affect?

CVE-2026-103620 affects enterprise server. Severity is medium (CVSS 6.5). 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 t

How urgent is CVE-2026-103620?

Priority 33/100. No elevated risk signals yet.

Software pages

GitHub vulnerabilities

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References

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