CVE-2026-126644
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Symlink Following in Ansible.posix Authorized Key Module

Vulnerability report for CVE-2026-126644, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.

Publication date: 2026-11-12

Last updated on: 2026-11-12

Assigner: redhat-SADP

Description

A link-following flaw was found in the authorized_key module of the ansible.posix collection, residual to the fix for CVE-2026-11837. That fix guards only the final path component (os.chown with follow_symlinks=False and O_NOFOLLOW in _safe_open_write()). When an unprivileged local user replaces their ~/.ssh directory with a symlink to a directory they do not own, and an operator subsequently runs the authorized_key task as root (a common provisioning pattern), the module resolves its path operations through the symlink: atomic_move() writes the temporary file in the symlink target and renames it to <target>/authorized_keys, creating or overwriting a file in the attacker-chosen directory, and os.chmod(sshdir, 0o700) follows the symlink and changes the target directory's permissions. The written file is chowned to the unprivileged user, so this is not a privilege escalation, but it allows an attacker to create or overwrite files (for example in /etc/apt/apt.conf.d/, which APT reads regardless of file ownership) to cause integrity and availability impacts.

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Meta Information

Published
2026-11-12
Last Modified
2026-11-12
Generated
2026-11-12
AI Q&A
2026-11-12
EPSS Evaluated
N/A
NVD
EUVD

Affected Vendors & Products

Showing 2 associated CPEs

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-59 The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

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Executive Summary

CVE-2026-126644 is a link-following flaw in the ansible.posix authorized_key module. It allows an attacker to replace their ~/.ssh directory with a symlink to a root-owned directory. When the authorized_key task runs as root, the module follows the symlink and writes files outside the intended directory, such as in /etc/apt/apt.conf.d/. This does not escalate privileges but can overwrite or create files, affecting system integrity and availability.

The vulnerability persists because prior fixes only protected the final path component, leaving parent-directory symlinks unguarded. Exploitation requires local access to set up the symlink and for the operator to run the module as root against attacker-controlled paths.

Detection Guidance

Check for unexpected symlinks in user home directories, particularly ~/.ssh. Use commands like 'find /home -type l -ls' to detect symlinks. Inspect /etc/apt/apt.conf.d/ for unauthorized files. Review ansible.posix authorized_key task logs for operations targeting modifiable directories.

Impact Analysis

This vulnerability can allow an attacker to overwrite or create files in unintended locations, such as /etc/apt/apt.conf.d/. This could disrupt system integrity and availability by modifying critical files. While it does not lead to privilege escalation, it can cause system instability or unexpected behavior.

Compliance Impact

This vulnerability could impact compliance with GDPR and HIPAA by allowing unauthorized file modifications in critical system directories. For GDPR, integrity violations may occur if attacker-controlled files alter system behavior, potentially affecting data processing. For HIPAA, file overwrites in directories like /etc/apt/apt.conf.d/ could disrupt security configurations or logging mechanisms, compromising protected health information integrity.

Mitigation Strategies

Avoid running the authorized_key module as root against directories users can modify. Verify target paths are not symlinks before operations. Ensure proper directory ownership and permissions. Update ansible.posix to the latest patched version if available.

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