CVE-2026-55158
Received Received - Intake

Conflibot Remote Code Execution via Pull Request

Publication date: 2026-09-15

Last updated on: 2026-09-15

Assigner: GitHub, Inc.

Description
Conflibot warns in advance when merging a pull request will cause conflicts in other open pull requests. Prior to 1.2.1, src/index.ts builds git checkout, git merge, and git format-patch commands by interpolating the attacker-controlled pull request head.ref value into strings passed to exec. In the documented pull_request_target configuration, an attacker can open a pull request, including from a fork, whose branch name contains shell metacharacters, and the workflow automatically interprets those characters as commands without maintainer interaction. The commands execute on a runner with base-repository secrets and a write-scoped GITHUB_TOKEN, allowing arbitrary command execution, secret or token exfiltration, unauthorized pushes, and other token abuse. The fixed implementations in src/index.ts and src/conflibot.ts use execFile or spawn argument arrays, and the v2 line also uses numeric pull-request refs rather than branch names. This issue is fixed in versions 1.2.1 and 2.0.0.

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Meta Information

Published
2026-09-15
Last Modified
2026-09-15
Generated
2026-09-15
AI Q&A
2026-09-15
EPSS Evaluated
N/A
NVD
CVE-2026-55158
EUVD
EUVD-2026-78769

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
github conflibot 1.2.1
github conflibot 2.0.0
wktk conflibot 1.2.1
wktk conflibot 2.0.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-78 The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

Attack-Flow Graph

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Executive Summary

CVE-2026-55158 is a command injection vulnerability in the conflibot GitHub Action. It occurs when the tool builds Git commands by inserting attacker-controlled branch names directly into shell strings. If a pull request's branch name contains shell metacharacters like backticks or semicolons, those characters are executed as commands when the workflow runs. This allows arbitrary code execution with the permissions of the GitHub token used by the workflow.

Detection Guidance

Check if conflibot versions before 1.2.1 or 2.0.0 are installed by running: npm list conflibot or checking package.json. Inspect workflow files for pull_request_target event usage with conflibot. Look for suspicious branch names in pull requests containing shell metacharacters like backticks, $(), ;, |, or &.

Impact Analysis

An attacker could exploit this to steal secrets, push unauthorized code, or perform other actions with the token's elevated permissions. The impact is highest when conflibot runs with the pull_request_target event, as it grants access to the base repository's secrets and a write-scoped token. Exploitation happens automatically when a crafted pull request is opened.

Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating confidentiality and integrity requirements in GDPR and HIPAA. If exploited, it may result in data breaches, unauthorized disclosure of personal or health information, or tampering with sensitive records, all of which are compliance violations.

Mitigation Strategies

Upgrade conflibot to version 1.2.1 or 2.0.0 immediately. Update workflow configurations to use the patched version. Avoid using pull_request_target event if possible. Review and remove any untrusted branch names in pull requests.

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