Vulnerability in py7zr (CVE-2026-55206)
Summary
Vulnerability in py7zr (CVE-2026-55206). Risk of unauthorized operations or information disclosure. 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. Prior to 1.1.3, PackInfo._read() in archiveinfo.py used an O(n^2) cumulative sum pattern for attacker-controlled numstreams values parsed from archive headers, allowing a crafted .7z archive to cause excessive CPU consumption during SevenZipFile.init() before extraction. This issue is 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-2026-55206 has been found in py7zr.
Risk of unauthorized operations or information disclosure.
What to do: upgrade py7zr to 1.1.3 or later.
If unsure, ask your IT team or search "py7zr CVE-2026-55206" on the vendor's site.
CVE-2026-55206 (py7zr) — CWE-407
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-407) exists in py7zr.
Check the vendor advisory for the affected versions of py7zr.
Severity: ?. Risk of unauthorized operations or information disclosure.
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-2026-55206 py7zr
- Ubuntu UBUNTU-CVE-2026-55206 py7zr
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- web github.com
- web github.com