CVE-2026-4296: An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attac

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HIGH 8.8UPGRADE

CVE-2026-4296 is a high-severity flaw (CVSS 8.8) affecting enterprise server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to bypass OAuth redirect URI validation. An attacker with knowledge of a first-party OAuth application's registered callback URL could craft a malicious authorization link that, when clicked by a victim, would redirect the OAuth authorization code to an attacker-controlled domain. This could allow the attacker to gain unauthorized acc

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 63%)
CISA exploited list	No
Weakness	CWE-185
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-2026-4296?

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-2026-4296 being exploited?

CVE-2026-4296 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-2026-4296 affect?

CVE-2026-4296 affects enterprise server. Severity is high (CVSS 8.8). An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to bypass OAuth redirect URI validation. An attacker with knowledge of a first-party OAuth application's registered callback U

How urgent is CVE-2026-4296?

Priority 40/100. High severity

Software pages

GitHub vulnerabilities

Related CVEs

CVE-2026-5921 HIGH 8.9 UPGRADE A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an
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CVE-2026-5845 CRITICAL 9.6 UPGRADE An improper authorization vulnerability in scoped user-to-server (ghu_) token authorization in GitHub Enterpri
CVE-2026-5512 MEDIUM 4.3 UPGRADE An improper authorization vulnerability was identified in GitHub Enterprise Server that allowed an authenticat
CVE-2026-8034 CRITICAL 9.8 UPGRADE A server-side request forgery (SSRF) vulnerability was identified in the GitHub Enterprise Server notebook vie

References

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