CVE-2026-73621VulnerabilityPublished 14 Aug 2026Updated 26 Oct 2026

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

Affects nbdimeSource GCVE Database

Authoritative record:CVE-2026-73621· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 4.0.4_6 when convenient.

Data as of 26 Oct 2026, 17:27 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 29% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.0.4_6

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade nbdime to 4.0.4_6.

Affected software

Product	Affected	Fixed in
Homebrewnbdime`pkg:brew/nbdime`Other threats	Affected >=1.1.0 <4.0.4_6	Fixed in 4.0.4_6

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available in GitPython version 4.0.4_6 that adds the missing check_unsafe_options guard to Commit.count(), preventing unsafe output argument injection. Users should upgrade to version 4.0.4_6 or later to remediate this vulnerability. Until patched, avoid passing untrusted input to Commit.count() keyword arguments that may be forwarded to git rev-list.

Description

GitPython versions up to 3.1.53 contain a vulnerability in the Commit.count() method where unguarded forwarding of options to git rev-list allows an attacker to specify an --output argument. This causes git rev-list to truncate an arbitrary file to zero bytes, leading to file destruction. The vulnerability is due to missing unsafe option checks in Commit.count(), unlike sibling methods that have such guards. The impact is medium severity as it allows file truncation at the process privilege level but does not allow content control or arbitrary file creation.

Impact

An attacker able to influence the arguments passed to Commit.count() can cause git rev-list to truncate an arbitrary file to zero bytes, resulting in loss of file integrity and availability at the privilege level of the running process. There is no control over the file content written, only truncation to zero bytes. This can disrupt applications or systems relying on the affected files. The vulnerability does not allow reading or arbitrary code execution.

Summary

The GitPython library's Commit.count() method forwards keyword arguments directly to git rev-list without checking for unsafe options. Specifically, passing an output parameter to count() results in git rev-list truncating the specified file to zero bytes before processing revisions. This behavior can be exploited to destroy or blank arbitrary files accessible by the process. The vulnerability exists in versions up to 3.1.53 and was verified by truncating a victim file. Unlike the guarded iter_commits() method, count() lacks the check_unsafe_options guard, making it an uncovered sink. The issue was fixed in version 4.0.4_6 by adding the necessary safety checks.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 17:27 UTC

Technical details

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