Vulnerability in py7zr (CVE-2026-23879)
Summary
Vulnerability in py7zr (CVE-2026-23879). Successful exploitation can lead to full system takeover. Exploitable via py7zr. Mitigation: upgrade to 1.1.3 or later.
Original description
The description as published by the source.
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.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-23879 has been found in py7zr.
Attackers can target a specific entry point like py7zr over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 8.0/10.
What to do: upgrade py7zr to 1.1.3 or later.
If unsure, ask your IT team or search "py7zr CVE-2026-23879" on the vendor's site.
CVE-2026-23879 (py7zr) — CWE-59 / CVSS v3 8.0
Attack vector: remote (network-reachable)
Attack surface: py7zr / extractall / output
Patched: 1.1.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-59) exists in py7zr. Attackers reach the vulnerable code path via py7zr.
Check the vendor advisory for the affected versions of py7zr. Attack surface: py7zr / extractall / output.
Severity: High (CVSS 8.0/10). Successful exploitation can lead to full system takeover.
Update to 1.1.3.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'py7zr' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'py7zr' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
py7zrを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade py7zr to 1.1.3ステージング環境で 1.1.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-23879 py7zr
- Ubuntu UBUNTU-CVE-2026-23879 py7zr
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- web github.com
- web github.com
- web pypi.org