Conflibot: Command injection via crafted pull request branch names under pull_request_target

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-55158
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-15 15:17:18 UTC
Updated2026-09-29 19:07:47 UTC
DescriptionConflibot 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.

Risk And Classification

Primary CVSS: v3.1 9.1 CRITICAL from [email protected]

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

EPSS: 0.008040000 probability, percentile 0.549970000 (date 2026-09-29)

Problem Types: CWE-78 | CWE-78 CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
3.1CNADECLARED9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Wktk Conflibot affected < 1.2.1 Not specified

References

ReferenceSourceLinkTags
github.com/wktk/conflibot/security/advisories/GHSA-2qvg-qr73-mqxp [email protected] github.com
github.com/wktk/conflibot/releases/tag/v2.0.0 [email protected] github.com
github.com/wktk/conflibot/commit/59e255c49c920fd6b67471ab9ef3bf194439a3f2 [email protected] github.com
github.com/wktk/conflibot/commit/0107ac6a4575ea200d0b92287ea58f975be9505d [email protected] github.com
github.com/wktk/conflibot/releases/tag/v1.2.1 [email protected] github.com
github.com/wktk/conflibot/pull/329 [email protected] github.com
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