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NVD / CVE Program· CNA GitHub_P

CVE-2026-2266: Improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed cross-site scripting via task list content and enabled ar

Noroxi assessment

Priority: Monitor (action score 29/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.21% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No special conditions are required; it is repeatable.
  • Fixed version: GitHub Enterprise Server 3.18.6, 3.19.3.

Low priority for now. Upgrade to GitHub Enterprise Server 3.18.6, 3.19.3 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.4 · v4.0—No exploit Fix available
Published
Mar 10, 2026
Updated
Jun 17, 2026
EPSS
0.2% · 11th percentile

Report tools

JSON

Action score

29

Monitor

Low priority for now.

CVSS
29 / 40 · 7.4 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_P
7.4
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-2266

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
githubenterprise server

Limit the impact of XSS

This is a cross-site scripting (XSS) vulnerability. A well-configured Content-Security-Policy doesn't fix it, but greatly reduces its impact. Check your site's CSP and other security headers for free.

Check security headers

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • github enterprise serverbefore 3.18.6
  • github enterprise server3.19.0 and later · before 3.19.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_P). Independent of NVD's CPE analysis and usually ahead of it.

  • GitHub Enterprise Server

    • 3.18.0 and later · up to and including 3.18.5affected · semverfixed in 3.18.6
    • 3.19.0 and later · up to and including 3.19.2affected · semverfixed in 3.19.3

Same product

github: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-0200Unsafe Reflection in Github Enterprise Server leading to Command Injection
    61This week
  • CVE-2024-0507Privilege Escalation by Code Injection in the Management Console in GitHub Enterprise Server
    55Plan
  • CVE-2026-3854Remote code execution via git push option injection in GitHub Enterprise Server
    47Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-1999Feb 18, 2026 · Incorrect Authorization vulnerability was identified in GitHub Enterprise Server that allowed unauthorized merging of pull requests
    28Monitor
  • ← EarlierCVE-2026-3306Mar 10, 2026 · Improper authorization in GitHub Projects allows modification of issue and pull request metadata without repository write access
    21Monitor
  • Later →CVE-2026-3582Mar 10, 2026 · Incorrect Authorization in GitHub Enterprise Server allows access to issue and commit search results without repo scope
    21Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
GitHub Enterprise Server3.18.6Vendor (CNA)
GitHub Enterprise Server3.19.3Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2025-1404689 days apartInsufficient HTML Sanitization Allows User-Controlled DOM Elements to Overwrite Server-Initialized Data Islands and Trigger Unintended Server-Side POST Requests
    34Monitor
  • CVE-2025-11892120 days apartDOM-based Cross-Site Scripting was identified in GitHub Enterprise Server Issues search allows privilege escalation and unauthorized workflow triggers
    34Monitor
  • CVE-2025-3246327 days apartMarkdown math block sanitization bypass allows privilege escalation and unauthorized workflow triggers
    34Monitor
  • CVE-2025-1374463 days apartImproper Neutralization of Input During Web Page Generation vulnerability was identified in GitHub Enterprise Server that allowed rendering of malicious HTML
    33Monitor
  • CVE-2026-77912196 days apartStored cross-site scripting vulnerability in GitHub Enterprise Server allowed HTML attribute injection via the Markdown rendering pipeline
    29Monitor
  • CVE-2026-10585112 days apartStored cross-site scripting vulnerability in GitHub Enterprise Server allowed arbitrary JavaScript execution via crafted Discussion titles in the Q&A category
    25Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

  • CVE-2026-860677 days apartServer-Side Request Forgery in GitHub Enterprise Server via Advisory Package URL Endpoint
    28Monitor
  • CVE-2026-673658 days apartAuthentication bypass vulnerability in GitHub Enterprise Server allowed creation of local user accounts bypassing the configured external identity provider
    25Monitor

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
P
Scope
X

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
commentEl.innerHTML = comment.body;

Fixed

ts
commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records