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Link Following (Symlink)Weakness · CWE-59

CVE-2026-23879

HIGH · 8.0 CVSS v3.1 Published 2026-06-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

py7zr versions 1.1.2 and below contain a symlink traversal vulnerability in extractall() that allows arbitrary file writes. The library validates the archive entry name but fails to properly resolve the combined symlink path, enabling malicious archives to create symlinks pointing outside the destination directory. Subsequent file extractions through these symlinks can write to arbitrary host locations.

MitigationUpgrade py7zr to version 1.1.3 or later to obtain the patch that properly validates resolved symlink targets before extraction.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify py7zr installation and version
    Run 'pip show py7zr' or check your project dependencies (requirements.txt, pyproject.toml, setup.py) for the py7zr version
    Affected if py7zr version is 1.1.2 or lower, or no version is specified (implying an unpatched version could be installed)
  2. Confirm extractall() method is in use
    Search your codebase for calls to py7zr.TarFile.extractall() or py7zr.SevenZipFile.extractall(), or inspect runtime calls to the library's extraction functions
    Affected if Your code calls extractall() to unpack 7z archives from untrusted sources
  3. Verify archive source trust level
    Review whether the extracted archives originate from untrusted or user-supplied sources (downloads, uploads, network transfers, email attachments)
    Affected if You extract archives from untrusted or external sources without prior validation
  4. Inspect for symlinks in extracted content
    After extraction, run 'find <extracted_dir> -type l -ls' on Linux or 'Get-ChildItem -Recurse -LinkType | Select-Object FullName' on Windows to list created symbolic links
    Affected if Any symbolic links in the extracted archive point to paths outside the intended extraction directory

You are affected if py7zr version 1.1.2 or lower is installed AND you use extractall() to unpack archives from untrusted or external sources, as the symlink traversal could allow writing files outside the destination directory.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade py7zr to version 1.1.3 or later to obtain the patch that properly validates resolved symlink targets before extraction.

Recommended fix High confidence

1.1.3

  1. Verify the current installed version of py7zr by running: pip show py7zr
  2. Upgrade py7zr to version 1.1.3 or later by running: pip install --upgrade py7zr==1.1.3
  3. Verify the upgrade was successful by running: pip show py7zr and confirming the version number

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,920
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-23879 in production — separate from our analysis above.

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