CVE-2026-15621: Clawlet Path Traversal Vulnerability

CVE-2026-15621 Overview

CVE-2026-15621 is a link following vulnerability [CWE-59] affecting mosaxiv clawlet versions up to 0.2.10. The flaw resides in the read_file, write_file, and edit_file functions within tools/fs_ops.go, which comprise the File Tools component. An attacker with local access and low privileges can manipulate symbolic links to cause the application to read, write, or modify files outside the intended scope.

The issue was reported publicly through GitHub, but the maintainer closed the corresponding issue with the label "not planned," indicating no vendor fix is expected.

Critical Impact
Local attackers can leverage symbolic link manipulation to read, overwrite, or modify sensitive files accessible to the clawlet process, breaching file confidentiality and integrity.

Affected Products

mosaxiv clawlet versions up to and including 0.2.10
Component: File Tools (tools/fs_ops.go)
Affected functions: read_file, write_file, edit_file

Discovery Timeline

2026-07-14 - CVE-2026-15621 published to NVD
2026-07-14 - Last updated in NVD database

Technical Details for CVE-2026-15621

Vulnerability Analysis

The vulnerability is a link following weakness classified under [CWE-59]. The read_file, write_file, and edit_file functions in tools/fs_ops.go operate on file paths without validating whether the target path is a symbolic link pointing outside the intended working directory.

When the application resolves a supplied path, it follows any symlinks present. An attacker who can place or influence files in a directory the tool operates on can redirect these file operations to arbitrary locations on the local file system. This allows unauthorized reads of sensitive files, overwriting of protected files, or tampering with configuration data accessible to the clawlet process.

Because the maintainer closed the GitHub issue as "not planned," this vulnerability remains unpatched and constitutes a permanent risk for any deployment running affected versions.

Root Cause

The root cause is missing validation of symbolic links before performing file I/O operations. The fs_ops.go file operations trust the resolved path returned by the operating system rather than verifying the canonical path stays within an allowed boundary. Safe implementations should call path canonicalization functions and reject paths that traverse outside a designated root directory.

Attack Vector

Exploitation requires local access with low privileges and no user interaction. The attacker must be able to influence files or paths within a directory processed by clawlet. By planting a symlink whose name matches a path the tool operates on, the attacker redirects read_file, write_file, or edit_file operations to a target of their choosing. See the GitHub PoC Repository and GitHub Issue Tracker for reference material.

No verified exploit code is available. The vulnerability is described in prose based on the VulDB CVE-2026-15621 entry.

Detection Methods for CVE-2026-15621

Indicators of Compromise

Unexpected symbolic links appearing inside directories processed by clawlet, particularly links pointing outside the working directory.
File modification timestamps on sensitive system or configuration files that correlate with clawlet activity in process logs.
Access denied or permission errors logged by clawlet when following links into privileged paths.

Detection Strategies

Monitor process file access events from the clawlet binary and flag open, openat, and readlink syscalls that resolve targets outside the expected working directory.
Audit file system telemetry for symlink and symlinkat calls made by non-root users in directories that clawlet later reads or writes.
Compare file paths supplied to clawlet against canonicalized paths to identify divergence indicative of symlink redirection.

Monitoring Recommendations

Enable Linux audit rules on directories used by clawlet to record symlink creation and modification events.
Ingest file system and process telemetry into a centralized logging platform for correlation with user session activity.
Alert on any invocation of clawlet by low-privilege users when the process subsequently accesses sensitive system paths such as /etc, /root, or user home directories outside the invoking user.

How to Mitigate CVE-2026-15621

Immediate Actions Required

Restrict execution of clawlet to trusted users only and remove it from multi-tenant systems where local low-privilege users are present.
Run clawlet inside a sandbox, container, or chroot environment that limits file system visibility to a dedicated directory tree.
Audit existing working directories used by clawlet and remove any symbolic links that should not be present.

Patch Information

No official patch is available. The maintainer closed the GitHub Issue Tracker report with the label "not planned," meaning the vendor does not intend to release a fix. Organizations should treat all versions up to 0.2.10 as permanently vulnerable and evaluate migration to alternative tooling or maintain a locally patched fork.

Workarounds

Wrap clawlet execution in a mandatory access control profile such as AppArmor or SELinux that restricts file access to an allow-listed directory.
Apply file system namespaces or bind mounts to present clawlet with a minimal, isolated view of the file system.
Set restrictive permissions (chmod 700) on directories used by clawlet so that other local users cannot plant symlinks.
Consider forking the project and adding a canonicalization check that rejects any resolved path outside the intended root.

bash

# Configuration example: constrain clawlet with a bind-mounted isolated directory
mkdir -p /var/lib/clawlet-jail
chmod 700 /var/lib/clawlet-jail
chown clawlet-user:clawlet-user /var/lib/clawlet-jail

# Run clawlet inside an unshared mount namespace with restricted view
unshare --mount --propagation private \
  sh -c 'mount --bind /var/lib/clawlet-jail /var/lib/clawlet-jail && \
         cd /var/lib/clawlet-jail && \
         exec /usr/local/bin/clawlet'