CVE-2026-77912Network attack vector

Stored XSS via post-sanitization quote rewriting

Published Sep 22, 2026 · Updated Sep 22, 2026

Stored XSS in GitHub Enterprise Server allows remote authenticated users to compromise viewers' sessions through crafted Markdown. The Markdown pipeline rewrites quote characters after sanitizing HTML and does not sanitize the transformed output again, enabling injected attributes to invoke same-origin JavaScript gadgets. Exploitation requires another user to view the stored content; resulting DOM access exposes visible data and CSRF tokens and permits state-changing actions with that viewer's authority.

CVSS severityUnavailable
Unscored
EPSS probability0.21%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in GitHub Enterprise Server allows remote authenticated users to compromise viewers' sessions through crafted Markdown. The Markdown pipeline rewrites quote characters after sanitizing HTML and does not sanitize the transformed output again, enabling injected attributes to invoke same-origin JavaScript gadgets. Exploitation requires another user to view the stored content; resulting DOM access exposes visible data and CSRF tokens and permits state-changing actions with that viewer's authority.

The record

CVE
CVE-2026-77912
Published
Sep 22, 2026
Updated
Sep 22, 2026
Vendor
Git LFS
Product
GitHub Enterprise Server
Classifications
T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.17.0 <3.17.* changes=[{"at":"3.17.21","status":"unaffected"}]
  2. Affected versionversion=3.18.0 <3.18.* changes=[{"at":"3.18.15","status":"unaffected"}]
  3. Affected versionversion=3.19.0 <3.19.* changes=[{"at":"3.19.12","status":"unaffected"}]
  4. Affected versionversion=3.20.0 <3.20.* changes=[{"at":"3.20.8","status":"unaffected"}]
  5. Affected versionversion=3.21.0 <3.21.* changes=[{"at":"3.21.6","status":"unaffected"}]
  6. Affected versionversion=3.22.0 <3.22.* changes=[{"at":"3.22.1","status":"unaffected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Git LFS · GitHub Enterprise Serverversion=3.17.0 <3.17.* changes=[{"at":"3.17.21","status":"unaffected"}]; version=3.18.0 <3.18.* changes=[{"at":"3.18.15","status":"unaffected"}]; version=3.19.0 <3.19.* changes=[{"at":"3.19.12","status":"unaffected"}]; version=3.20.0 <3.20.* changes=[{"at":"3.20.8","status":"unaffected"}]; version=3.21.0 <3.21.* changes=[{"at":"3.21.6","status":"unaffected"}]; version=3.22.0 <3.22.* changes=[{"at":"3.22.1","status":"unaffected"}]

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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