Vulnerability in dfir-unfurl (CVE-2026-40036)
Summary
Vulnerability in dfir-unfurl (CVE-2026-40036). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 20260405 or later.
Original description
The description as published by the source.
Summary
The compressed data parser uses zlib.decompress() without a maximum output size. A small, highly compressed payload can expand to a very large output, causing memory exhaustion and denial of service.
Details
unfurl/parsers/parse_compressed.pycallszlib.decompress(decoded)with no size limit.- Inputs are accepted from URL components that match base64 patterns.
- Highly compressible payloads can expand orders of magnitude larger than their compressed size.
PoC
- Generate a payload with
security_poc/poc_decompression_bomb.py --generate-only. - The script creates a base64-encoded zlib payload embedded in a URL.
- Submitting the URL to
/json/visjscan cause the server to allocate large amounts of memory. - The script includes a
--testmode but warns it can crash the service.
PoC Script
#!/usr/bin/env python3
"""
Unfurl Decompression Bomb Proof of Concept
==========================================
This PoC demonstrates a Denial of Service vulnerability in Unfurl's
compressed data parsing. The zlib.decompress() call has no size limits,
allowing an attacker to submit small payloads that expand to gigabytes.
Vulnerability Location:
- parse_compressed.py:81-82:
inflated_bytes = zlib.decompress(decoded) # No maxsize parameter
Attack Impact:
- Memory exhaustion
- Service crash
- Resource consumption (cloud cost attacks)
Usage:
python poc_decompression_bomb.py [--target URL] [--size SIZE_MB]
"""
import argparse
import…
Source: NIST National Vulnerability Database 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-2026-40036 has been found in dfir-unfurl.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade dfir-unfurl to 20260405 or later.
If unsure, ask your IT team or search "dfir-unfurl CVE-2026-40036" on the vendor's site.
CVE-2026-40036 (dfir-unfurl) — CWE-409 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 20260405 — 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-409) exists in dfir-unfurl.
Check the vendor advisory for the affected versions of dfir-unfurl.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 20260405.
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 'dfir-unfurl' . 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
-
1Identify exposure identify
grep -r 'dfir-unfurl' . | 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
dfir-unfurl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 dfir-unfurl to 20260405ステージング環境で 20260405 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
References
- advisory disclosure@vulncheck.com
- advisory nvd.nist.gov
- advisory github.com
- exploit disclosure@vulncheck.com
- package github.com
- package pypi.org
- web disclosure@vulncheck.com
- web github.com
- web github.com
- web github.com