CVE-2026-87819VulnerabilityPublished 20 Sep 2026Updated 26 Oct 2026

cf2tf · GitPython: Denial of Service via catastrophic backtracking (ReDoS) in Actor.name_email_regex — commit author/committer

Affects cf2tfSource GCVE Database

Authoritative record:CVE-2026-87819· High 8.7

Not known to be exploited · CVSS 8.7 High : upgrade to 0.9.2_9 soon.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 4.0 base score

8.7High

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 43% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.9.2_9

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
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: 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: None: There is no loss of integrity within 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 cf2tf to 0.9.2_9.

Affected software

Product	Affected	Fixed in
Homebrewcf2tf`pkg:brew/cf2tf`Other threats	Affected >=0.6.1 <0.9.2_9	Fixed in 0.9.2_9

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

Description

### Summary GitPython's `Actor.name_email_regex` regular expression (`git/util.py`, line 863) is vulnerable to catastrophic backtracking (ReDoS — Regular Expression Denial of Service). When GitPython parses the `author` or `committer` header of a git commit object that contains a long string with an unterminated `<` (no matching `>`), the Python regex engine enters quadratic backtracking, causing complete single-threaded CPU exhaustion proportional to the square of the input length. A single crafted commit object can block any GitPython API call that reads `.author` or `.committer` for **over two minutes per invocation**, enabling denial of service against CI runners, code-hosting backends, repository-scanning pipelines, or any service that processes commits from third-party or untrusted repositories. --- ### Details **Vulnerable file and line:** `git/util.py`, line 863: ```python name_email_regex = re.compile(r"(.*) <(.*?)>") ``` This regex is evaluated inside `Actor._from_string()` (line 909) every time GitPython resolves a commit's `.author` or `.committer` property. **Full call chain — from public API to vulnerable sink:** commit.author # any ordinary GitPython API call └── git/objects/commit.py:917 Commit._deserialize() └── git/objects/util.py:341 parse_actor_and_date(author_line) └── git/util.py:909 Actor._from_string(string) └── Actor.name_email_regex.search(string) ← VULNERABLE `author_line` is decoded directly from the raw bytes of the git commit object with **no length limit, character restriction, or timeout** applied at any point before reaching the regex engine. The same chain is triggered by: - `commit.author` - `commit.committer` - `repo.iter_commits()` - `repo.blame()` - Any web service / CI tool that displays or processes commit metadata **Why this pattern backtracks catastrophically:** The pattern `(.*) <(.*?)>` contains an unbounded greedy group `(.*)` followed by a literal space and `<`. When the input is a long string that contains `<` but no closing `>`, the regex engine must try every possible split position for the greedy group — O(n²) candidate positions for a string of length n — each of which then drives the inner lazy group into further sub-match attempts. This is the well-documented "catastrophic backtracking" failure mode for this family of patterns. **Empirically measured scaling (tested against GitPython 3.1.59, commit 52a6cba):** | Author field length (bytes) | Time to resolve `.author` | |-----------------------------|--------------------------| | 1,000 | 0.0035 s | | 5,000 | 0.084 s | | 10,000 | 0.341 s | | 20,000 | 1.525 s | | 40,000 | 5.963 s | | 60,000 | 13.360 s | | 80,000 | 23.871 s | | **200,000** | **150.488 s** | Each doubling of input size roughly quadruples processing time (e.g. 40,000 → 80,000 bytes: 5.96 s → 23.87 s ≈ 4.0×), confirming O(n²) growth. Git itself imposes **no practical size limit** on author name fields in the object format. **How the malicious object reaches a victim:** The PoC creates the commit object as a correctly SHA-1-hashed, zlib-compressed git loose object written directly into `.git/objects/`. `git cat-file -t <sha>` confirms it is a valid `commit` type and git's own read-side tools display it without error. Only git's write-side tooling (`git commit --author`, `git update-index`, explicit `git fsck`) applies the sanity checks that would reject a malformed author line. Delivery paths that bypass those checks include: - A git server with `receive.fsckObjects = false` (common in self-hosted deployments) - A `.git` directory shipped as a tarball, backup, or zip archive - A git bundle file - Any automated mirror or import tool that operates at the object level --- ### PoC **Environment used for testing:** - GitPython 3.1.59, installed in editable mode from source (no code modifications) - Python 3.12.3, git 2.43.0, Ubuntu 24.04 **Script 1 — craft the malicious repository (`craft_malicious_repo.py`):** ```python #!/usr/bin/env python3 """ Creates a git repository with one commit whose 'author' field is a large string containing an unterminated '<'. Bypasses git's write-side sanity checks by writing the raw object directly into .git/objects/. Usage: python3 craft_malicious_repo.py <target_dir> <payload_size_bytes> """ import hashlib, os, subprocess, sys, zlib def run(cmd, cwd): return subprocess.run(cmd, cwd=cwd, check=True, capture_output=True, text=True) def main(): if len(sys.argv) != 3: print(f"usage: {sys.argv[0]} <target_dir> <payload_size_bytes>") sys.exit(1) target_dir, payload_size = sys.argv[1], int(sys.argv[2]) os.makedirs(target_dir, exist_ok=True) run(["git", "init", "--quiet"], cwd=target_dir) run(["git", "config", "user.email", "poc@example.com"], cwd=target_dir) run(["git", "config", "user.name", "PoC"], cwd=target_dir) with open(os.path.join(target_dir, "README.txt"), "w") as f: f.write("GitPython ReDoS PoC repository\n") run(

References

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