GHSA-p538-c434-8v24 CVE-2026-73621 PYSEC-2026-3950

GitPython: Arbitrary file truncation via git rev-list --output argument injection in unguarded Commit.count

Medium PyPI

Severity: 0.0 / 10; Medium · CVSS 4.0
Exploit chance (EPSS): 0.36%; Chance of exploitation in the next 30 days. Higher than 29.84% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-88 Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
Fix: 3.1.56; Upgrade gitpython to this version or later

Description

Summary

Commit.count() forwards **kwargs into rev_list with no check_unsafe_options guard (the guard exists only in the sibling iter_items, commit.py:341). git rev-list --output=<path> opens and truncates the target file to 0 bytes before revision parsing, so count(output='/victim') destroys/blanks an arbitrary file.

Root Cause

commit.py:290-291 calls self.repo.git.rev_list(self.hexsha, **kwargs) with no check_unsafe_options and no allow_unsafe_options parameter. The sibling iter_items (commit.py:341) is guarded; count is not. This is a distinct, uncovered sink — GHSA-956x-8gvw-wg5v fixed iter_commits/blame, not count.

Impact

Destroy/blank an arbitrary file at process privilege (integrity/availability). Reachability is key-control only (count uses self.hexsha, not a user ref), and the write is a 0-byte truncation (no content control), so MEDIUM.

Proof of Concept

commit.count(output='/path/to/victim')   # victim truncated to 0 bytes (verified)
# control: commit.iter_commits(output=...) raises UnsafeOptionError

Attack Chain

Entry: app forwards user options -> commit.count(output='/victim'). Guard: none. Bypass proof: iter_commits(output=) raises UnsafeOptionError; count(output=) does not — verified side-by-side.
Sink: git rev-list <sha> --output=/victim -> file truncated to 0 bytes. Impact: destroy/blank arbitrary file.

Bypass Evidence

Live-verified on HEAD (tag 3.1.53): count(output=<victim>) truncated a pre-existing file to 0 bytes; guarded iter_commits(output=) raised UnsafeOptionError. Same CNA-accepted "app forwards user options dict" model as GHSA-956x-8gvw-wg5v's archive(**kwargs). Uncovered sink, not a duplicate.

Affected Versions

<= 3.1.53

Suggested Fix

Add check_unsafe_options to Commit.count (mirroring iter_items).

Reported by zx (Jace) — GitHub: @manus-use

Affected versions

PyPI

Package	Vulnerable	Fixed in
gitpython	`< 3.1.56`	`3.1.56`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

gitpython PyPI → `3.1.56`

pip

pip install --upgrade "gitpython>=3.1.56"

poetry

poetry add "gitpython>=3.1.56"

uv

uv add "gitpython>=3.1.56"

Severity breakdown

CVSS 4.0 0.0

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack vector: Network
Attack complexity: Low
Attack requirements: None
Privileges required: Low
User interaction: None
Confidentiality (vulnerable system): None
Integrity (vulnerable system): Low
Availability (vulnerable system): Low
Confidentiality (subsequent systems): None
Integrity (subsequent systems): None
Availability (subsequent systems): None
Exploit maturity: Not defined
Scope: X

CVSS 3.1 5.4

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

Attack vector: Network
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: Low

Weakness

CWE-88: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.

How to prevent it

Implementation: Where possible, avoid building a single string that contains the command and its arguments. Some languages or frameworks have functions that support specifying independent arguments, e.g. as an array, which is used to automatically perform the appropriate quoting or escaping while building the command. For example, in PHP, escapeshellarg() can be used to escape a single argument to system(), or exec() can be called with an array of arguments. In C, code can often be refactored from using system() - which accepts a single string - to using exec(), which requires separate function arguments for each parameter.
Architecture and Design: Understand all the potential areas where untrusted inputs can enter your product: parameters or arguments, cookies, anything read from the network, environment variables, request headers as well as content, URL components, e-mail, files, databases, and any external systems that provide data to the application. Perform input validation at well-defined interfaces.
Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Implementation: Directly convert your input type into the expected data type, such as using a conversion function that translates a string into a number. After converting to the expected data type, ensure that the input's values fall within the expected range of allowable values and that multi-field consistencies are maintained.
Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control. Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.
Implementation: When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.
Implementation: When your application combines data from multiple sources, perform the validation after the sources have been combined. The individual data elements may pass the validation step but violate the intended restrictions after they have been combined.
Testing: Use dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

References

Advisories

vulncheck.com/advisories/gitpython-before-arbitrary-file-truncation-via-commit-count

Packages

github.com/gitpython-developers/GitPython

Timeline

Aug 3, 2026 Published
Oct 24, 2026 Last updated by the source
Oct 31, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-83vg-56qc-22m7 GitPython validates a submodule's ".git" path only after cloning into it (RCE)	High	Also affects gitpython
GHSA-gq48-pqfc-9p58 GitPython: Submodule.move() follows an attacker-committed intermediate symlink outside the worktree	Medium	Also affects gitpython
GHSA-23mf-xhv8-69c2 GitPython: arbitrary file read via attacker-controlled branch name in `Head.checkout()` (incomplete fix of CVE-2026-78679)	High	Also affects gitpython
GHSA-f9j4-qggq-h239 GitPython Remote.pull() refspec bypasses the --upload-pack unsafe-option guard, enabling arbitrary command execution	Critical	Also affects gitpython
GHSA-w8jc-g24h-crhw GitPython command wrappers omit unsafe protocol and option checks	High	Also affects gitpython
GHSA-m64x-33q8-m5h7 GitPython parse_actor_and_date() is vulnerable to quadratic backtracking on malformed identity lines	High	Also affects gitpython
GHSA-fx3j-rwgx-fr94 GitPython: separate_git_dir leaks env vars via crafted .gitmodules submodule name	High	Also affects gitpython
GHSA-59cr-6r3x-644w GitPython submodule update path traversal can write outside the repository	Medium	Also affects gitpython

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