GitPython CVE-2026-73624

Exploitation requires that an application using GitPython passes attacker-controlled data to any Diffable.diff() call site - specifically to the other positional parameter or to any keyword argument, most directly output. The value-control injection path requires only that the caller accept a user-supplied revision string for other, with no additional keyword argument needed, making it the lower-friction of the two paths. The CVSS 4.0 PR:L metric indicates authenticated application access is required; unauthenticated exploitation against the library is not modeled by the provided vector, and exploitability depends entirely on whether the hosting application exposes diff functionality to lower-trust users. The content written to the overwritten file is git diff/patch output partially shaped by repository state - not free-form arbitrary bytes - but per the vendor advisory, controlling the destination path alone is sufficient for a High integrity impact. File-system impact is bounded by the OS-level permissions of the process account running Python; on hardened deployments where the process runs as a restricted service account with a narrow writable file set, the blast radius is correspondingly smaller.

The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N) characterizes this as a network-reachable, low-complexity flaw exploitable by any authenticated low-privileged application user who can trigger a diff operation - no special attack prerequisites exist beyond that access. Integrity and availability are both rated High (VI:H/VA:H), reflecting the ability to overwrite arbitrary files reachable by the process, such as SSH authorized_keys, configuration files, or lock files, and thereby enable persistence, credential theft, or service disruption. No EPSS score was included in the source intelligence package; however, the existence of a vendor-confirmed, live-verified proof-of-concept raises practical exploitation probability well above what the absence of KEV listing might suggest. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog at time of analysis, indicating no confirmed mass exploitation, but the low attack complexity and available PoC compress the window before that changes - even a mid-sized municipal IT team in zabrze running a self-hosted code review platform or CI/CD pipeline that exposes diff operations to authenticated users should treat this as urgent rather than deferring to a routine patch cycle. Impact is scoped to the vulnerable process's file system (SC:N/SI:N/SA:N), which limits lateral scope change to downstream systems but does not diminish the severity of what an attacker can accomplish within that boundary on a typical deployment.

An attacker with authenticated low-privileged access to a web-based code review or CI/CD platform built on GitPython submits a crafted revision reference - for example, --output=/home/app/.ssh/authorized_keys - as the other argument to a diff endpoint. GitPython constructs a git diff-tree subprocess command inserting this value before the -- separator, causing git to open, truncate, and write diff-tree output to the SSH authorized_keys file. With a public proof-of-concept confirmed against tag 3.1.53, an attacker can reliably overwrite the target file with attacker-influenced diff content, enabling SSH key injection or configuration corruption at the process's privilege level.