Unfurl < 2026.04 - Denial of Service via Unbounded zlib Decompression (CVE-2026-40036) | HOL Guard CVE

High · CVSS 8.7CVE-2026-40036

Unfurl < 2026.04 - Denial of Service via Unbounded zlib Decompression

Answer in brief

CVE-2026-40036 records a High severity (CVSS 8.7) vulnerability in Unfurl < 2026.04 - Denial of Service via Unbounded zlib Decompression. The current sources do not mark it as known exploited. The current feed maps obsidianforensics/unfurl (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Apr 8, 2026Updated Sep 24, 2026Source checked Sep 24, 2026First seen by HOL Sep 24, 2026Material review Sep 24, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps obsidianforensics/unfurl (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
obsidianforensics/unfurlgeneric	>=0 <2026.04	2026.04

Recommended response

Check inventory. Check lockfiles and deployed manifests for obsidianforensics/unfurl.
Review the reported fix. Update obsidianforensics/unfurl to 2026.04 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Apr 8, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 24, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.