CVE-2026-23879 py7zr: Arbitrary File Write Vulnerability
Attackers can write arbitrary files outside the extraction directory via malicious symbolic links, potentially leading to code execution or privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-23879?
CVE-2026-23879 is a high-severity path traversal vulnerability in miurahr py7zr, published on 24 Jun 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and decryption. Versions 1.1.2 and below contain an an arbitrary file write vulnerability, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using extractall to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. During extraction, the program only checks the link arcname within the destination directory, but ignores the combined symlink path resolution. Attackers can exploit this vulnerability by constructing malicious archives, thereby bypassing the directory boundary restrictions implemented by the extractor. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service. This issue has been fixed in version 1.1.3.
Weakness: CWE-59
Which versions are affected by CVE-2026-23879?
3 open source packages ship an affected version, including py7zr.
| Package | Affected | Fixed in |
|---|---|---|
py7zr PyPI | All versions | 1.1.3 |
py7zr PyPI | All versions | 1.1.3 |
py7zr PyPI | All versions | 1.1.3 |
How do I fix CVE-2026-23879?
Upgrade py7zr to 1.1.3 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-23879 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-23879 exists.
Sources
Also known as DEBIAN-CVE-2026-23879, GHSA-q6rc-2cgv-63h7, PYSEC-2026-2974, UBUNTU-CVE-2026-23879.