CVE-2026-77912

Description

A stored cross-site scripting (XSS) vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to inject arbitrary HTML attributes into rendered Markdown because the Markdown rendering pipeline rewrote quote characters in already-sanitized HTML without re-sanitizing the result. Crafted Markdown could abuse same-origin JavaScript gadgets to bypass Content Security Policy and gain control of the page DOM when viewed by another user. Successful exploitation could allow an attacker to read content visible to the victim, extract embedded CSRF tokens, perform state-changing actions as the victim, and exfiltrate data through same-origin writes. The payload could also propagate to repositories and organizations where the victim had write access. This vulnerability affected supported GitHub Enterprise Server releases in the 3.17, 3.18, 3.19, 3.20, 3.21, and 3.22 series and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported via the GitHub Bug Bounty program.

Overview

State: PUBLISHED
Assigner (CNA): GitHub_P
CVSS severity: HIGH
CVSS score: 7.4 / 10
CVSS vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N/AU:Y
Effective score: 7.4 / 10 HIGH source: CNA overview
CWE(s): CWE-79
Reserved: 2026-08-21
Published: 2026-09-22 20:43 UTC
Last updated: 2026-09-22 20:43 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/77xxx/CVE-2026-77912.json
Linked Threat: CVE-2026-77912 — Stored cross-site scripting vulnerability in GitHub Enterprise Server allowed HTML attribute injection via the Markdown rendering pipeline

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-09-22 21:17:32 UTC
NVD last modified: 2026-09-22 21:17:32 UTC

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-84873
Assigner: GitHub_P
Published: Sep 22, 2026, 8:43:56 PM
Updated: Sep 22, 2026, 8:43:56 PM
EUVD base score (CVSS 4.0): 7.4 / 10
CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N/AU:Y
EUVD-reported EPSS: 0.0000
Vendors: GitHub
Products: Enterprise Server (3.22.0 <3.22.*)

Enterprise Server (3.21.0 <3.21.*)

Enterprise Server (3.19.0 <3.19.*)

Enterprise Server (3.17.0 <3.17.*)

Enterprise Server (3.18.0 <3.18.*)

Enterprise Server (3.20.0 <3.20.*)
Aliases: GHSA-6293-4rx2-2p57

ENISA description: A stored cross-site scripting (XSS) vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to inject arbitrary HTML attributes into rendered Markdown because the Markdown rendering pipeline rewrote quote characters in already-sanitized HTML without re-sanitizing the result. Crafted Markdown could abuse same-origin JavaScript gadgets to bypass Content Security Policy and gain control of the page DOM when viewed by another user. Successful exploitation could allow an attacker to read content visible to the victim, extract embedded CSRF tokens, perform state-changing actions as the victim, and exfiltrate data through same-origin writes. The payload could also propagate to repositories and organizations where the victim had write access. This vulnerability affected supported GitHub Enterprise Server releases in the 3.17, 3.18, 3.19, 3.20, 3.21, and 3.22 series and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported via the GitHub Bug Bounty program.

EUVD references (6)

Affected products (1)

Vendor	Product	Versions	Platforms
GitHub	Enterprise Server	`3.17.0` (affected), `3.18.0` (affected), `3.19.0` (affected), `3.20.0` (affected), `3.21.0` (affected), `3.22.0` (affected)	—

Vendor references (6)

References embedded in the original CVE record by the assigning CNA.

https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.21 release-notes
https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.15 release-notes
https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.12 release-notes
https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.8 release-notes
https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.6 release-notes
https://docs.github.com/en/enterprise-server@3.22/admin/release-notes#3.22.1 release-notes

Web references (0)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

No web references attached yet.

NVD-tagged references (6)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.21 product-cna@github.com
https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.15 product-cna@github.com
https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.12 product-cna@github.com
https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.8 product-cna@github.com
https://docs.github.com/en/enterprise-server@3.21/admin/release-notes#3.21.6 product-cna@github.com
https://docs.github.com/en/enterprise-server@3.22/admin/release-notes#3.22.1 product-cna@github.com

Remediations (10)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

Oracle Security Critical Patch Update (CSPU) August 2026 for Oracle Java SE

web:docs.oracle.com

Oracle Security Critical Patch Update (CSPU) August 2026 for Oracle Java SE Services: Java Management Release Date: August 18, 2026 Java Management supports the following releases that are part of the Oracle Security Critical Patch Update (CSPU) August 2026 for Oracle Java SE:

2026-09-23 15:15 UTC
Pennsylvania Access To Criminal History - Home - pa

web:epatch.pa.gov

Why does PATCH exist? Its purpose is to better enable the public to obtain criminal history record checks. The repository was created and is maintained in accordance with Pennsylvania's Criminal History Information Act contained in Chapter 91 of Title 18, Crimes Code. This Act also directs the Pennsylvania State Police (PSP) to disseminate criminal history data to criminal justice agencies ...

2026-09-23 15:15 UTC
Patch - Everything Local: Breaking News, Events, Discussions

web:patch.com

The best breaking news, stories, and events from the Patch network of local news sites

2026-09-23 15:15 UTC
Joliet News, Breaking News in Joliet, IL - Patch

web:patch.com

Joliet Latest Headlines: 'No Kings Get Out The Vote' Rally For Joliet Revealed: 'Bring Your Poster With Your Feelings About Trump' ; 🌱 Patch AM: 2 Men Tried Switching Seats Before Joliet ...

2026-09-23 15:15 UTC
VALORANT Patch Notes 13.06

web:playvalorant.com

VALORANT's big update is here. TL;DR: The big one is here. A new home and lobby experience, Agent Mastery system, Gauntlet: Glitched, Practice Range in Queue, The Warden, Competitive Updates, and more are ALL LAUNCHING TODAY! Sup, gamers?! It's Kenny here to break down our biggest patch of the year—ok, maybe it's the biggest patch of the last few years. Maybe ever? Idk. Anyway, sit ...

2026-09-23 15:15 UTC
August 11, 2026—Hotpatch KB5120994 (OS Builds 26200.9106 and 26100.9106 ...

web:support.microsoft.com

This Hotpatch update for Windows 11, version 25H2 and 24H2 (KB5120994) includes security improvements. To learn more about differences between security updates, optional non-security preview updates, out-of-band (OOB) updates, and continuous innovation, see Windows monthly updates explained. For information on Windows update terminology, see the different types of Windows software updates. To ...

2026-09-23 15:15 UTC
Patch 1.0.15 - Valheim

web:valheim.com

We have a small patch today that fixes an issue which has caused some players to have duplicated terrains and decreased performance.

2026-09-23 15:15 UTC
Home - The Patch Augusta Municipal Golf Course

web:www.golfthepatch.com

Now open, The Patch features a redesigned 18-hole course, led by golf course architects Tom Fazio and Beau Welling, and a new 9-hole short course, The Loop at The Patch , designed by Tiger Woods and TGR Design. Welcome to Augusta's best-in-class public golf experience.

2026-09-23 15:15 UTC
Critical Patch Updates, Critical Security Patch Updates ... - Oracle

web:www.oracle.com

Critical Patch Updates Critical Patch Updates provide security patches for supported Oracle on-premises products. A Critical Patch Update is a collection of patches for multiple security vulnerabilities. These patches address vulnerabilities in Oracle code and in third party components included in Oracle products. These patches are usually ...

2026-09-23 15:15 UTC
Oracle

web:www.oracle.com

Oracle Critical Security Patch Update Advisory - August 2026 Description. A Critical Security Patch Update (CSPU) provides targeted, high-priority security fixes in a smaller, mor

2026-09-23 15:15 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-77912.json.

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