VulnerabilityPublished 20 Sep 2026Updated 26 Oct 2026

CVE-2026-87817: GitPython · Repository content can impersonate the git directory, leading to arbitrary code execution

Affects nbdimeSource GCVE Database

Authoritative record:CVE-2026-87817· High 8.7

Not known to be exploited · CVSS 8.7 High : upgrade to 4.0.4_8 soon.

Data as of 26 Oct 2026, 17:28 UTC

CVSS 4.0 base score

8.7High

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 35% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.0.4_8

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Passive
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: High
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: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
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 9 Sep 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_8.

Affected software

Product	Affected	Fixed in
Homebrewnbdime`pkg:brew/nbdime`Other threats	Affected >=1.1.0 <4.0.4_8	Fixed in 4.0.4_8

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

AI-suggested

A fix is available in GitPython version 4.0.4_8. Users should upgrade to this version or later to remediate the vulnerability. The fix includes reordering the git directory discovery to test the real .git directory first, validating HEAD contents, resolving hook paths via the common_dir, and disabling merge_includes in config reading. Until patched, avoid opening or cloning untrusted repositories with GitPython and performing commits via index.commit().

Description

GitPython version 3.1.59 contains a vulnerability where it incorrectly resolves the git directory path, allowing attacker-controlled repository content to impersonate the .git directory. This misresolution leads to execution of attacker-supplied hooks during a commit operation, arbitrary file reads outside the repository via crafted config files, and potential writes to attacker-chosen locations. The issue arises because GitPython tests certain files before the actual .git directory, causing it to treat the working tree root as the git directory. This flaw affects services that open or clone untrusted repositories using GitPython and perform commits via its native index.commit() method.

Impact

An attacker controlling repository content can cause arbitrary command execution on a victim system that opens or clones the repository with GitPython and performs a commit via index.commit(). Additionally, the attacker can read sensitive files outside the repository by crafting config files with include directives, and write config files to arbitrary locations. The attack is silent, passing git clone and git fsck checks without detection. This affects CI runners, code scanning, mirrors, dependency bots, and AI code review tools using vulnerable GitPython versions.

Summary

GitPython's Repo.__init__ method determines the git directory by testing candidate paths in an order that considers the real .git directory last. Two earlier tests can be satisfied by ordinary tracked files named gitdir, commondir, and HEAD at the repository root, which are legal tracked content in git. Consequently, GitPython resolves git_dir to the working-tree root instead of the actual .git directory. This causes all operations that treat files as inside the git directory, including executing hooks, to operate on attacker-controlled files. The vulnerability allows arbitrary code execution when a victim calls index.commit(), reading of files outside the repository via crafted config includes, and writing config files to attacker-chosen directories. The flaw is present in GitPython 3.1.59 and was demonstrated with a proof-of-concept that runs hooks from tracked files without detection by git fsck or other probes. The root cause is the discovery loop testing files in an unsafe order and lack of validation of HEAD contents. The real git client is unaffected. Remediation involves reordering the discovery to test .git first, validating HEAD contents, resolving hook paths properly, and disabling merge_includes in config reading. A fix is available in version 4.0.4_8.

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Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 17:28 UTC

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