Unsafe configuration options in GitHub Pages leading to remote code execution on GitHub Enterprise Server

published 2021-03-23 5y ago modified 2026-06-17 4mo ago also EUVD-2021-9999

cvss: 8.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 2.6%; EPSS 2.6% chance of exploitation in 30 days, percentile 85%
public exploits: 0; none known

A remote code execution vulnerability was identified in GitHub Enterprise Server that could be exploited when building a GitHub Pages site. User-controlled configuration options used by GitHub Pages were not sufficiently restricted and made it possible to override environment variables leading to code execution on the GitHub Enterprise Server instance. To exploit this vulnerability, an attacker would need permission to create and build a GitHub Pages site on the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.0.3 and was fixed in 3.0.3, 2.22.9, and 2.21.17. This vulnerability was reported via the GitHub Bug Bounty program.

Patch / fix

fixed in 1

GitHub GitHub Enterprise Server 2.21.17, 2.22.9, 3.0.3

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Exploit prediction

2.55% chance of exploitation in the next 30 days, higher than 85% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.1	8.8	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD	2.0	6.5	AV:N/AC:L/Au:S/C:P/I:P/A:P

Affected products

GitHub GitHub Enterprise Server

Classification

Weakness

CWE-77 Improper Neutralization of Special Elements used in a Command

References

Sources

CVE List CVE-2021-22864
NVD CVE-2021-22864

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