CVE-2026-122136 in Powerlevel10k
Summary
by MITRE • 11/04/2026
Powerlevel10k before 1.20.19 contains a symlink following vulnerability in _p9k_dump_instant_prompt that allows local attackers to overwrite victim-writable files via a predictable temporary path. Attackers can pre-plant symlinks at p10k-instant-prompt-output-<user>-<pid> in TMPDIR, guessing the victim's shell PID, so shell startup truncates and overwrites targeted files.
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Analysis
by VulDB Data Team • 11/04/2026
The vulnerability identified in Powerlevel10k versions prior to 1.20.19 represents a classic race condition combined with insecure temporary file handling, specifically categorized under CWE-59: Improper Link Resolution Before File Access or CWE-377: Insecure Temporary File. This flaw resides within the _p9k_dump_instant_prompt function, which is responsible for generating and caching instant prompt configurations to accelerate shell startup times. The core technical deficiency lies in the creation of temporary files using a predictable naming convention that incorporates the user's name and process identifier without employing secure randomization or atomic file operations. By constructing paths such as p10k-instant-prompt-output-<user>-<pid> within the system's TMPDIR, the script exposes itself to symlink following attacks where an attacker can manipulate the filesystem structure before the legitimate application writes its data.
From a technical perspective, this vulnerability exploits the time-of-check-to-time-of-use gap inherent in many shell scripts that do not utilize secure temporary file creation APIs like mktemp with appropriate flags or O_EXCL open modes. An adversary operating on the same local system can pre-plant symbolic links at the predicted path location within the TMPDIR directory. When the victim initiates their shell session, Powerlevel10k attempts to write the instant prompt output to this specific temporary file. Because the symlink already exists and points to a target of the attacker's choosing, typically a writable file owned by the victim or another critical system resource, the write operation effectively redirects data into that targeted location rather than creating a new isolated temporary file. This mechanism allows for arbitrary file overwrite operations with the privileges of the shell process executing Powerlevel10k.
The operational impact of this vulnerability is significant in multi-user environments or shared systems where local privilege escalation or denial-of-service scenarios are possible. An attacker who successfully exploits this flaw can truncate and overwrite victim-writable files, potentially leading to credential theft if configuration files containing sensitive data are targeted, or system instability if critical binaries or scripts are corrupted. In the context of ATT&CK framework tactics, this behavior aligns with T1564: Host File System Obfuscation through symlink manipulation and can facilitate T1078: Valid Accounts by compromising user-specific configurations to maintain persistence or escalate privileges. The predictability of the PID makes exploitation feasible for local attackers who have sufficient access to monitor process creation events, although it requires careful timing relative to the shell startup sequence.
Mitigation strategies primarily involve upgrading Powerlevel10k to version 1.20.19 or later, where developers have addressed this insecure temporary file handling by implementing secure randomization of temporary filenames and ensuring atomic operations that prevent symlink following attacks. For environments unable to upgrade immediately, administrators should enforce strict permissions on TMPDIR directories to restrict write access only to the respective user and consider using tmpfs mounts with noexec options if feasible. Additionally, auditing shell startup scripts for similar patterns of predictable temporary file usage across other installed plugins or custom configurations is recommended to prevent analogous vulnerabilities from being exploited through different vectors within the same environment.