CVE-2026-4821

Description

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.

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CVSS v3.1 Score

7.2

HIGH

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0004

Probability of exploitation

0.11%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-78 OS Command Injection

Affected Products

Vendor	Product	Versions
github	enterprise_server	< 3.14.26
github	enterprise_server	3.15.0 — 3.15.21
github	enterprise_server	3.16.0 — 3.16.17
github	enterprise_server	3.17.0 — 3.17.14
github	enterprise_server	3.18.0 — 3.18.8
github	enterprise_server	3.19.0 — 3.19.5
github	enterprise_server	All

References

Advisories & Patches

https://docs.github.com/en/[email protected]/admin/release-notes#3.14.24 https://docs.github.com/en/[email protected]/admin/release-notes#3.15.21 https://docs.github.com/en/[email protected]/admin/release-notes#3.16.17 https://docs.github.com/en/[email protected]/admin/release-notes#3.17.14 https://docs.github.com/en/[email protected]/admin/release-notes#3.18.8 https://docs.github.com/en/[email protected]/admin/release-notes#3.19.5 https://docs.github.com/en/[email protected]/admin/release-notes#3.20.1

Frequently Asked Questions

What is CVE-2026-4821? +

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. It has a CVSS v3.1 base score of 7.2 (HIGH).

How severe is CVE-2026-4821? +

CVE-2026-4821 has a CVSS v3.1 score of 7.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0004, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-4821? +

CVE-2026-4821 affects products from github, specifically: enterprise_server. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-4821? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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