---
id: CVE-2026-40036
title: Unfurl < 2026.04 - Denial of Service via Unbounded zlib Decompression
summary: "Unfurl before\_2026.04 contains an unbounded zlib decompression vulnerability in parse_compressed.py that allows remote attackers to cause denial of service. Attackers can submit highly compressed payloads via URL parameters to the /json/…"
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-770
  - CWE-409
vendor: obsidianforensics
product: dfir-unfurl
affected:
  - dfir-unfurl < 2026.04
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-04-11T03:05:38.819397Z'
exploitAvailable: true
published: '2026-04-08'
updated: '2026-09-24'
sourceUpdated: '2026-09-24T14:17:36.037Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-40036'
references:
  - url: >-
      https://github.com/obsidianforensics/unfurl/security/advisories/GHSA-h5qv-qjv4-pc5m
    label: GHSA Advisory GHSA-h5qv-qjv4-pc5m
  - url: 'https://github.com/obsidianforensics/unfurl/releases/tag/v2026.04'
    label: >-
      VulnCheck Advisory: dfir-unfurl - Denial of Service via Unbounded zlib
      Decompression
  - url: >-
      https://www.vulncheck.com/advisories/dfir-unfurl-denial-of-service-via-unbounded-zlib-decompression
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-40036'
  - url: 'https://github.com/RyanDFIR/unfurl/pull/243'
  - url: >-
      https://github.com/RyanDFIR/unfurl/commit/7cc711a65b106742a21080b755f81c17b5725aa8
  - url: 'https://github.com/RyanDFIR/unfurl/releases/tag/v2026.04'
  - url: 'https://github.com/obsidianforensics/unfurl'
tags:
  - cve.org
  - exploit-available
  - osv
  - pip
epss: 0.0079
epssPercentile: 0.54326
aliases:
  - GHSA-h5qv-qjv4-pc5m
  - PYSEC-2026-1294
ecosystem: pip
patched:
  - dfir-unfurl 20260405
ingestedAt: '2026-07-08T18:25:49.989Z'
---

## Overview

Unfurl before 2026.04 contains an unbounded zlib decompression vulnerability in parse_compressed.py that allows remote attackers to cause denial of service. Attackers can submit highly compressed payloads via URL parameters to the /json/visjs endpoint that expand to gigabytes, exhausting server memory and crashing the service.

## Affected

- `dfir-unfurl < 2026.04`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-40036)

Affected packages:

- `dfir-unfurl < 20260405`

Patched in:

- `dfir-unfurl 20260405`

Source: https://osv.dev/vulnerability/GHSA-h5qv-qjv4-pc5m