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Enterprise ServerApplication · GitHub

CVE-2026-8034

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-07
Fix available
A fix is available. Upgrade to 3.16.18 / 3.17.15 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A server-side request forgery (SSRF) vulnerability was identified in the GitHub Enterprise Server notebook viewer that allowed an attacker to access internal services by exploiting URL parser confusion between the validation layer and the HTTP request library. The hostname validation used a different URL parser than the request library, enabling a crafted URL to pass validation while directing the request to an unintended host. Exploitation required network access to the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.16.18, 3.17.15, 3.18.9, 3.19.6, and 3.20.2. This vulnerability was reported via the GitHub Bug Bounty program.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A server-side request forgery (SSRF) vulnerability in GitHub Enterprise Server's notebook viewer exploits URL parser inconsistency—validation uses a different parser than the HTTP request library, allowing crafted URLs to bypass hostname checks while actually targeting internal services.

MitigationUpgrade GitHub Enterprise Server to version 3.16.18, 3.17.15, 3.18.9, 3.19.6, 3.20.2 or later to patch the vulnerability; restrict network access to internal services as a defense-in-depth measure.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Enterprise ServerApplication
Affected:< 3.16.18>= 3.17.0, < 3.17.15>= 3.18.0, < 3.18.9>= 3.19.0, < 3.19.6>= 3.20.0, < 3.20.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify GitHub Enterprise Server version
    Access the GitHub Enterprise Server admin console or run 'ghe-version' from the management shell to retrieve the installed version number
    Affected if The installed version falls within any vulnerable range: < 3.16.18; >= 3.17.0 and < 3.17.15; >= 3.18.0 and < 3.18.9; >= 3.19.0 and < 3.19.6; >= 3.20.0 and < 3.20.2
  2. Verify notebook viewer is accessible
    Check Site Admin settings for the notebook feature or inspect if the /notebooks endpoint is available to users
    Affected if The notebook viewer feature is enabled and accessible to users who could supply crafted URLs to trigger the SSRF
  3. Confirm network exposure of internal services
    Review security group settings, firewall rules, and internal networkACLs to determine if the GitHub Enterprise Server host can reach internal services on non-public IPs
    Affected if The server can initiate HTTP connections to internal network addresses (RFC 1918, link-local) which an attacker could target via the notebook viewer URL parser bypass

You are affected if your GitHub Enterprise Server version is within the vulnerable ranges AND the notebook viewer feature is enabled AND internal network services are reachable from the GitHub host.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.16.18 / 3.17.15 / 3.18.9 or later
Fixed in 3.16.183.17.153.18.9
Interim mitigation

Upgrade GitHub Enterprise Server to version 3.16.18, 3.17.15, 3.18.9, 3.19.6, 3.20.2 or later to patch the vulnerability; restrict network access to internal services as a defense-in-depth measure.

Recommended fix High confidence

Upgrade to version 3.16.18, 3.17.15, 3.18.9, 3.19.6, or 3.20.2 or later (recommended)

  1. 1. Identify the currently installed GitHub Enterprise Server version using the administrative web interface or administrative shell.
  2. 2. Determine the appropriate upgrade path based on current version: if < 3.16.18, upgrade to 3.16.18; if >= 3.17.0 and < 3.17.15, upgrade to 3.17.15; if >= 3.18.0 and < 3.18.9, upgrade to 3.18.9; if >= 3.19.0 and < 3.19.6, upgrade to 3.19.6.
  3. 3. Review the GitHub Enterprise Server upgrade prerequisites and backup requirements in the official documentation.
  4. 4. Perform a backup of the GitHub Enterprise Server instance as recommended in the upgrade guide.
  5. 5. Download the appropriate upgrade package from the GitHub Enterprise Server downloads page.
  6. 6. Follow the standard upgrade procedure for GitHub Enterprise Server, either via the administrative web interface or command-line utilities.
  7. 7. After upgrade completion, verify the notebook viewer functionality and confirm the version number reflects the patched release.
  8. 8. Validate that the SSRF vulnerability is mitigated by testing that internal services are no longer accessible via crafted URLs in the notebook viewer.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Enterprise Server Scoped from the published advisory
  • Consultation3.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA3.0 h
18.0 hours of engineering $3,180
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-8034 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data