CVE-2026-19118 in GitHub
Summary
by MITRE • 09/01/2026
A time-of-check time-of-use race condition vulnerability was identified in GitHub Enterprise Server that allowed remote code execution. Exploitation required an authenticated user with write access to a repository and precise timing of concurrent upload requests. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.17.20, 3.18.14, 3.19.11, 3.20.7, 3.21.5, and 3.22.0. This vulnerability was reported via the GitHub Bug Bounty program.
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Analysis
by VulDB Data Team • 09/02/2026
A critical time-of-check to time-of-use race condition vulnerability has been identified within GitHub Enterprise Server, presenting a severe risk of remote code execution for authenticated attackers. This flaw stems from a fundamental synchronization failure in how the application handles concurrent file upload operations. Specifically, the security check verifying user permissions and file validity is performed at one point in time, but the actual use or processing of that data occurs later without re-verification under race conditions. An attacker with write access to a repository can exploit this window by submitting multiple simultaneous upload requests designed to manipulate internal state variables before the system completes its initial validation logic. This allows malicious payloads to bypass intended security controls and execute arbitrary code on the server infrastructure, potentially leading to full compromise of the enterprise environment.
The operational impact of this vulnerability is significant due to the high privilege level required for exploitation combined with the technical complexity involved in achieving successful timing attacks. While an attacker must possess authenticated access with write permissions to a repository, which limits the pool of potential initial vectors compared to unauthenticated exploits, the ability to achieve remote code execution elevates the severity substantially. Successful exploitation could allow adversaries to exfiltrate sensitive intellectual property, install persistent backdoors, pivot laterally across internal networks, or disrupt service availability through resource exhaustion or destructive commands. The vulnerability affected all versions of GitHub Enterprise Server prior to version 3.22, indicating a systemic issue in the upload handling mechanism that persisted across multiple major releases until it was addressed.
Mitigation strategies primarily involve immediate patching to one of the fixed release branches. Organizations running vulnerable instances must upgrade to GitHub Enterprise Server version 3.17.20, 3.18.14, 3.19.11, 3.20.7, 3.21.5, or any subsequent version including 3.22 and later where the race condition has been resolved through improved synchronization primitives and validation logic. In addition to patching, administrators should enforce strict access controls by adhering to the principle of least privilege, ensuring that write permissions are granted only to trusted users and automated systems with verified identities. Implementing rate limiting on upload endpoints can also reduce the likelihood of successful race condition exploitation by making it more difficult for attackers to coordinate precise concurrent requests.
From a classification perspective, this vulnerability aligns closely with CWE-367, which defines time-of-check time-of-use (TOCTOU) race conditions as errors in multi-threaded or distributed systems where checking and using data are not atomic operations. The exploitation technique also maps to MITRE ATT&CK techniques related to privilege escalation and command-line interface abuse, specifically leveraging local application logic flaws to gain higher-level access than originally intended. This incident underscores the importance of rigorous concurrency testing during software development life cycles and highlights how subtle timing discrepancies in web applications can lead to catastrophic security failures when combined with authenticated user privileges.