CVE-2026-109349 in gix-pack
Summary
by MITRE • 10/12/2026
gitoxide gix-pack before 0.75.0 contains a reachable assertion in BytesToEntriesIter::new_from_header: the pack header decoder accepts version 3, but a release-enabled assert_eq! requires version 2. A malicious remote can send a 12-byte pack header declaring version 3 to panic the client and abort the clone or fetch.
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Analysis
by VulDB Data Team • 10/12/2026
The vulnerability identified in gitoxide versions prior to 0.75.0 represents a critical reliability flaw within the gix-pack component, specifically affecting the logic responsible for parsing Git packfile headers. This issue manifests as a reachable assertion failure during the initialization of the BytesToEntriesIter structure via its new_from_header method. The core technical deficiency lies in an inconsistency between the validation logic and the actual implementation constraints. While the pack header decoder is designed to accept version 3 of the Git pack format, which was introduced to support larger objects and improved compression efficiency, a release-enabled assert_eq! macro strictly enforces that the parsed version must equal two. This mismatch creates a scenario where valid input according to one part of the system triggers an immediate panic in another, violating the principle of graceful error handling expected in robust software systems.
From an operational perspective, this vulnerability allows for a remote denial-of-service attack against users interacting with malicious Git repositories. An attacker can craft a specially constructed packfile header that declares version 3 and transmit it to a victim machine performing a clone or fetch operation using the affected gitoxide library. Upon receiving this malformed input, the application will encounter an unrecoverable panic condition during the parsing phase. This results in the abrupt termination of the Git client process, effectively denying service to the user who is attempting to retrieve code artifacts. Unlike typical software bugs that might return error codes or corrupt data, assertion failures lead to immediate crashes, making this a straightforward vector for disrupting development workflows and CI/CD pipelines that rely on automated fetching mechanisms.
The classification of this vulnerability aligns with CWE-617, which describes Reachable Assertion, indicating that the program logic allows an attacker to trigger a condition that causes the application to abort unexpectedly. In terms of offensive security frameworks such as MITRE ATT&CK, this behavior is consistent with techniques used in Denial of Service attacks where availability is compromised by exploiting software weaknesses rather than overwhelming resources through volume. The attack vector is classified as Remote because it requires network interaction with a malicious server hosting the crafted packfile, and it exploits the Trust Boundary between the client application and external data sources without requiring authentication or prior access to the victim system.
Mitigation strategies for this vulnerability primarily involve updating the gitoxide library to version 0.75.0 or later, where the assertion logic has been corrected to properly handle version 3 headers in accordance with the Git specification. For organizations unable to immediately update dependencies, implementing input validation at a higher level of the application stack can provide temporary relief by rejecting packfiles that do not conform to expected versions before they reach the vulnerable parsing module. Additionally, developers should ensure that their CI/CD environments and internal tooling are updated to prevent exposure to untrusted repositories or to utilize alternative Git libraries if gitoxide remains in use without immediate patching. Regular auditing of third-party dependencies for assertion-related flaws is recommended as part of a comprehensive software supply chain security posture.