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Fencer Vulns
high 8.0

CVE-2026-23879 json

py7zr: Arbitrary File Write Vulnerability

published 2026-06-19 4 mo ago modified 2026-10-25 14 d ago also EUVD-2026-39050 , GHSA-q6rc-2cgv-63h7 , PYSEC-2026-2974

cvss
8.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi py7zr 1.1.3
  • py7zr_project py7zr 1.1.3
  • py7zr Debian 14 1.1.2+dfsg-1

debian advisories DEBIAN-CVE-2026-23879

  • python-py7zr openSUSE Leap 16.0 1.0.0-bp160.2.1
  • python-py7zr openSUSE Tumbleweed 1.1.3-1.1

opensuse advisories openSUSE-SU-2026:21159-1openSUSE-SU-2026:11112-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-23879 updated cvss 8.0

py7zr: py7zr: Arbitrary file write via crafted symbolic links during archive extraction

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
4 mo ago

Exploit prediction

0.50% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/miurahr/py7zr/security/advisories/GHSA-q6rc-2cgv-63h7 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.0 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
GitHub 3.1 8.0 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
OSV 3.1 8.0 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
pypi py7zr
<1.1.3
1.1.3

Affected products

  • miurahr py7zr

Classification

Weakness
  • CWE-59 Improper Link Resolution Before File Access

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.