PT-2026-34210 · Github · Enterprise Server

Seokchan Yoon · Published 2026-04-21 · Updated 2026-04-24 · CVE-2026-4821

Mitre

CVSS v4.0

8.1

High

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

An improper neutralization of special elements vulnerability was identified in GitHub Enterprise Server that allowed an authenticated Management Console administrator to execute arbitrary OS commands via shell metacharacter injection in proxy configuration fields such as http proxy. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and administrator privileges to the Management Console. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program.

Fix

RCE

OS Command Injection

Weakness Enumeration

CWE-78

Related Identifiers

CVE-2026-4821

Affected Products

Enterprise Server

References · 9

• https://nvd.nist.gov/vuln/detail/CVE-2026-4821 · Security Note
• https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.8 · Note
• https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.1 · Note
• https://twitter.com/_seokchan_yoon/status/2047470957863018652 · Twitter Post
• https://docs.github.com/en/enterprise-server@3.14/admin/release-notes#3.14.24 · Note
• https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.14 · Note
• https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.17 · Note
• https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.5 · Note
• https://docs.github.com/en/enterprise-server@3.15/admin/release-notes#3.15.21 · Note