CVE-2026-56236: Capgo CLI Path Traversal Vulnerability

CVE-2026-56236 Overview

CVE-2026-56236 affects Capgo CLI versions prior to 12.128.2. The vulnerability stems from unsafe file operations in login and build credential handling routines. These routines follow symbolic links without validation, classified under [CWE-59] (Improper Link Resolution Before File Access).

An attacker who controls a repository can plant malicious symlinks that the CLI will follow during normal developer operations. This allows arbitrary file overwrite on the developer machine or exposure of credential files with world-readable permissions. Exploitation requires a developer to run the CLI inside an attacker-controlled repository, making this a supply chain risk for projects that consume untrusted Capgo configurations.

Critical Impact
Local attackers can overwrite arbitrary files or leak Capgo credentials by tricking developers into running the CLI against a repository containing crafted symlinks.

Affected Products

Capgo CLI versions prior to 12.128.2
Developer workstations executing capgo login operations
Build pipelines invoking Capgo credential operations against untrusted repositories

Discovery Timeline

2026-06-21 - CVE-2026-56236 published to NVD
2026-06-22 - Last updated in NVD database

Technical Details for CVE-2026-56236

Vulnerability Analysis

The Capgo CLI performs credential read and write operations during login and build workflows. The implementation opens target paths using standard file APIs without checking whether intermediate path components or the final target are symbolic links. When the CLI writes to a path such as a credentials cache or log file, the operating system transparently resolves any symlink and writes to the symlink's target instead.

This behavior provides a classic symlink attack primitive [CWE-59]. An attacker who can place files inside a repository can substitute expected output paths with links pointing to sensitive locations on disk. When a developer clones the repository and runs the CLI, the tool writes attacker-controlled content to those targets under the developer's privileges.

A second variant of the flaw involves credential file creation with overly permissive modes. Files containing Capgo authentication material are created world-readable, allowing any local user on a multi-tenant system to read tokens belonging to another account.

Root Cause

The root cause is missing link validation in the credential I/O paths. The CLI does not call lstat to detect symlinks before opening files, nor does it use O_NOFOLLOW flags when invoking open. File creation routines also omit explicit restrictive permission modes such as 0600, falling back to a permissive default umask result.

Attack Vector

The attack vector is local with required user interaction. An attacker prepares a public repository containing symlinks in paths the Capgo CLI writes to, then convinces a developer to clone the project and run a Capgo command. The CLI follows the symlinks, overwriting arbitrary files the developer's account can modify or exposing freshly written credential files to other local users.

Detection Methods for CVE-2026-56236

Indicators of Compromise

Unexpected modifications to files outside the working repository after Capgo CLI execution
Capgo credential files present with world-readable permissions (-rw-r--r-- or broader)
Symbolic links inside cloned repositories that point to paths under $HOME, /etc, or build system directories
Capgo CLI invocations in CI logs that target repositories from untrusted sources

Detection Strategies

Audit installed Capgo CLI versions across developer endpoints and build agents; flag any version below 12.128.2
Scan repositories before execution for symbolic links using find . -type l and review their targets
Monitor file integrity on developer home directories for writes initiated by node or capgo processes outside expected paths

Monitoring Recommendations

Log process execution of the Capgo CLI binary along with the working directory at invocation time
Alert on creation of files containing token-like strings with permission modes wider than 0600
Track CI/CD jobs that invoke Capgo commands against forked or external repositories

How to Mitigate CVE-2026-56236

Immediate Actions Required

Upgrade Capgo CLI to version 12.128.2 or later on all developer workstations and build agents
Rotate any Capgo authentication tokens that may have been written by a vulnerable CLI version
Review build pipelines for execution of the CLI against repositories that accept external contributions

Patch Information

The maintainers addressed the issue in Capgo CLI 12.128.2. Fix details are documented in the GitHub Security Advisory GHSA-8mpm-q7mh-8fvh and the VulnCheck Arbitrary File Overwrite Advisory. Update via the package manager used to install the CLI.

Workarounds

Avoid running the Capgo CLI inside repositories from untrusted sources until the upgrade is applied
Manually inspect repositories for symlinks before invoking any Capgo command
Restrict permissions on the Capgo credential directory to the current user only using chmod 700

bash

# Configuration example
npm install -g @capgo/cli@latest
capgo --version  # verify >= 12.128.2
chmod 700 ~/.capgo
find . -type l -exec ls -la {} \;  # audit repo for symlinks before CLI use