CVE-2026-114134
Description
A flaw was found in the Black GitHub Action. When configured to read project settings from a configuration file, the action fails to validate the specified version identifier. A remote attacker capable of submitting a pull request can supply a reference to external malicious code, leading to arbitrary code execution within the victim repository's continuous integration (CI) workflow environment.
Statement
This vulnerability is rated as Important because an untrusted contributor submitting a pull request can achieve arbitrary code execution inside the build runner environment without requiring administrative privileges. Red Hat enterprise products do not distribute or execute the upstream GitHub Action, and standalone deployments of the Black formatting utility on Red Hat platforms remain unaffected by this flaw. The exposure is confined strictly to external automated continuous integration workflows configured to load version specifications dynamically from repository files.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
--- CME Mitigation Guidance (2026-11-06) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to prevent pip from installing arbitrary package references by validating version specifiers passed to the Black GitHub Action runner: upgrade to Black 26.10.1, which validate the required-version string against a regular expression (BLACK_VERSION_RE) and reject invalid version specifiers or direct URL references with an error, closing all 3 injection vectors (crafted pyproject.toml tool.black.required-version configuration, direct URL package reference injection, untrusted pull request triggering CI workflow). Until patched, this is only a concern on GitHub Actions CI workflows running Black with use_pyproject enabled — Standalone Black CLI deployments and Red Hat enterprise products are unaffected — so Disable use_pyproject in Black GitHub Action configurations or restrict pull requests from untrusted contributors from triggering automated CI workflows that evaluate pyproject.toml. As a compensating measure, Deploy EDR agents to detect and quarantine suspicious child process execution and post-exploitation behavior launched by malicious Python setup scripts inside the CI runner environment and Deploy Falco or eBPF runtime security to detect anomalous child processes, unexpected shell spawns, or unauthorized outbound network connections within CI container runners during package installation. These controls limit blast radius and contain exploitation, but they do not fix the underlying unvalidated version specification defect — apply the upstream patch to fully remediate.
Highest-impact CME: CME-1001 EDR Agent (Endpoint Detection & Response) (medium)
Understanding the Weakness (CWE)
Confidentiality,Integrity,Availability
Technical Impact: Execute Unauthorized Code or Commands
An attacker could insert malicious functionality into the program by causing the program to download code that the attacker has placed into the untrusted control sphere, such as a malicious web site. This could enable the injection of malware, information exposure by granting excessive privileges or permissions to the untrusted functionality, DOM-based XSS vulnerabilities, stealing user's cookies, open redirect to malware (CWE-601), etc.
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