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CVE-2026-3854 represents a critical remote code execution vulnerability residing within the core git push processing pipeline of GitHub Enterprise Server.
The flaw stems from improper sanitization and handling of user-supplied push option values processed during repository update hooks.
Attackers with authenticated push access can chain specialized malicious payloads through multiple custom push option arguments.
These injected values manipulate internal environment variables and metadata fields during the pre-receive and post-receive hook execution phases.
Normally, enterprise installations rely on robust sandboxing mechanisms to isolate user scripts and prevent host-level command execution.
However, the lack of rigorous input validation allows these crafted push options to break out of the designated container sandbox constraints.
Consequently, arbitrary system commands run with elevated privileges directly on the underlying server architecture.
Exploitation does not require prior administrative rights, but it does mandate valid repository write permissions to trigger the hook pipeline.
Security researchers discovered that secondary parameters interact directly with internal execution environments without adequate stripping of control characters.
When the server parses these unvalidated strings, the command interpreter interprets them as executable directives rather than literal text.
This bypasses security boundary controls designed to restrict git hook capabilities to safe, predefined operations.
Organizations running unpatched instances face immediate risks of complete infrastructure compromise and unauthorized data tampering.
The vulnerability underscores the complex challenges of securely handling multi-tenant inputs within complex CI/CD and repository management pipelines.
Mitigation requires immediate patching or application of strict environment variable filtering across all affected enterprise deployment nodes.
Continuous log auditing for anomalous semicolons or command separators in push options remains vital for detecting early reconnaissance attempts.
DailyCVE Form:
Platform: GitHub Enterprise Server
Version: Prior to 3.20.0
Vulnerability: Remote Code Execution
Severity: Critical Level
date: April 28 2026
Prediction: Already Patched Officially
What Undercode Say:
git push -o "malicious_payload=true; id" origin main tail -n 100 /var/log/github-audit.log | grep ";"
import subprocess
def simulate_push_option(option_string):
sanitized = option_string.replace(";", "").replace("&", "")
return sanitized
Exploit: (Educational Purposes!)
To understand the mechanics of CVE-2026-3854, an attacker constructs a malicious git push command embedding shell control operators inside push options (-o). When GitHub Enterprise Server processes these options during hook invocation, the lack of input neutralization allows the shell to interpret the injected characters. This leads to arbitrary command execution within the server environment. Security analysts study this vector to ensure hooks are strictly sandboxed and parameters are escaped before execution.
Protection: from this CVE
Administrators must immediately upgrade GitHub Enterprise Server to patched versions (3.14.25, 3.15.20, 3.16.17, 3.19.4, 3.20.0, or later). Review audit logs for suspicious push operations containing command separators or semicolons in push options. Restrict repository push access strictly to trusted personnel and enforce the principle of least privilege across all project workflows.
Impact:
Successful exploitation grants an attacker full remote code execution capabilities on the underlying host system. This can lead to total compromise of the GitHub Enterprise Server instance, unauthorized access to private source code repositories, data exfiltration, lateral movement within the corporate network, and persistent system disruption.
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Sources:
Reported By: github.com
Extra Source Hub:
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