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Enterprise ServerApplication · GitHub

CVE-2026-2266

MEDIUM · 5.4 CVSS v3.1 Published 2026-03-10
Fix available
A fix is available. Upgrade to 3.18.6 / 3.19.3 or later.
See remediation →
58/100
Remediation priority · Elevated
Remotely reachable

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
An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed DOM-based cross-site scripting via task list content. The task list content extraction logic did not properly re-encode browser-decoded text nodes before rendering, allowing user-supplied HTML to be injected into the page. An authenticated attacker could craft malicious task list items in issues or pull requests to execute arbitrary scripts in the context of another user's browser session. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.20 and was fixed in versions 3.18.6 and 3.19.3. 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

DOM-based XSS vulnerability in GitHub Enterprise Server's task list feature. The task list content extraction logic fails to properly re-encode browser-decoded text nodes before rendering, allowing authenticated attackers to inject malicious HTML via crafted task list items in issues or pull requests. When viewed by other users, this enables arbitrary script execution in their browser session.

MitigationUpgrade GitHub Enterprise Server to version 3.18.6, 3.19.3, or later. These patched versions include proper re-encoding of text nodes in task list content before DOM insertion.

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:< 3.18.6>= 3.19.0, < 3.19.3

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
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

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 administrative interface or run 'ghe-version' command in the management shell to determine the installed version
    Affected if The installed version is lower than 3.18.6 OR falls between 3.19.0 and 3.19.3 (inclusive)
  2. Verify task list feature availability
    Confirm access to issues or pull requests in any repository, as the task list feature is built into these areas
    Affected if The task list feature is accessible (this is the default state in GitHub Enterprise Server)
  3. Confirm user authentication capability
    Verify ability to create or edit issues or pull requests, which requires authenticated access to the GitHub Enterprise Server instance
    Affected if Authenticated users can interact with issues or pull requests containing task lists

The environment is affected if the GitHub Enterprise Server version falls within the vulnerable ranges (< 3.18.6 or >= 3.19.0 and < 3.19.3) and the task list feature in issues or pull requests is accessible to authenticated users.

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 3.18.6 / 3.19.3 or later
Fixed in 3.18.63.19.3
Interim mitigation

Upgrade GitHub Enterprise Server to version 3.18.6, 3.19.3, or later. These patched versions include proper re-encoding of text nodes in task list content before DOM insertion.

Recommended fix High confidence

3.18.6, 3.19.3, or 3.20+ (latest stable release)

  1. Identify the current GitHub Enterprise Server version by checking the administrative dashboard or running 'ghe-version' command
  2. If running version < 3.18.6: upgrade to version 3.18.6 or later
  3. If running version >= 3.19.0 and < 3.19.3: upgrade to version 3.19.3 or later
  4. If running any version prior to 3.20: upgrade to version 3.20 or the latest stable release
  5. After upgrade, verify the fix by ensuring task list content in issues and pull requests is properly sanitized

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

Fix this in Enterprise Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
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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-2026-2266 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
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