CVE-2026-4821
Shell Metacharacter Injection in GitHub Enterprise Server Proxy Configuration
Publication date: 2026-04-21
Last updated on: 2026-04-29
Assigner: GitHub, Inc. (Products Only)
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| github | enterprise_server | to 3.14.26 (exc) |
| github | enterprise_server | From 3.15.0 (inc) to 3.15.21 (exc) |
| github | enterprise_server | From 3.16.0 (inc) to 3.16.17 (exc) |
| github | enterprise_server | From 3.17.0 (inc) to 3.17.14 (exc) |
| github | enterprise_server | From 3.18.0 (inc) to 3.18.8 (exc) |
| github | enterprise_server | From 3.19.0 (inc) to 3.19.5 (exc) |
| github | enterprise_server | 3.20.0 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-78 | The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability is an improper neutralization of special elements in GitHub Enterprise Server. It allows an authenticated Management Console administrator to execute arbitrary operating system commands by injecting shell metacharacters into proxy configuration fields such as http_proxy.
Exploitation requires both access to the GitHub Enterprise Server instance and administrator privileges to the Management Console.
The issue affects all versions of GitHub Enterprise Server prior to 3.21 and was fixed in several versions starting from 3.14.26 up to 3.20.1.
How can this vulnerability impact me? :
If exploited, this vulnerability allows an attacker with administrator access to execute arbitrary OS commands on the server hosting GitHub Enterprise Server.
This can lead to unauthorized control over the server, potentially compromising the confidentiality, integrity, and availability of the system and its data.
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, you should upgrade your GitHub Enterprise Server to a fixed version. The vulnerability affects all versions prior to 3.21 and is fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, and 3.14.26.
Additionally, restrict access to the Management Console to trusted administrators only, as exploitation requires administrator privileges.