CVE-2026-5921: A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an

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HIGH 8.9REMOTEUPGRADE

CVE-2026-5921 is a high-severity flaw (CVSS 8.9) affecting enterprise server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook rendering service. When private mode was disabled, the notebook viewer followed HTTP redirects without revalidating the destination host, enabling an unauthenticated SSRF to internal services. By chaining this wi

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	8.9 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Weakness	CWE-918
Published	2026-04-21
Last modified	2026-10-26

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

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-21 23:16 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

github enterprise server UPGRADE

Affected: < 3.14.26 · >= 3.15.0 and < 3.15.21 · >= 3.16.0 and < 3.16.17 · >= 3.17.0 and < 3.17.14 · >= 3.18.0 and < 3.18.8 · >= 3.19.0 and < 3.19.5 · 3.20.0

Fixed in: 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5

Safe to downgrade to: a release before 3.15.0

1. Check installed version

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

2. UPGRADE to 3.14.26 (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 3.15.0 (Debian / Ubuntu)

apt-cache madison enterprise-server sudo apt install enterprise-server=<VERSION_BEFORE_3.15.0> 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_3.15.0> 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-2026-5921?

enterprise server: upgrade to 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5. Exact commands for each OS are on this page.

Is CVE-2026-5921 being exploited?

CVE-2026-5921 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-2026-5921 affect?

CVE-2026-5921 affects enterprise server. Severity is high (CVSS 8.9). A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook re

How urgent is CVE-2026-5921?

Priority 45/100. High severity; Remotely exploitable, no login, no user action

Software pages

GitHub vulnerabilities

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References

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