CVE-2026-40036Public exploitNetwork attack vector

Service crash via unbounded zlib decompression

Published Apr 8, 2026 · Updated Apr 8, 2026

Unbounded zlib decompression in Obsidian Forensics Unfurl before 2026.04 allows remote attackers to crash the service via a crafted URL. parse_compressed.py passes base64-decoded URL data to zlib.decompress() without limiting its output, allowing a small input to expand to gigabytes. No authentication or user interaction is required; deployment memory and URL-length limits determine whether resource exhaustion crashes the process.

CVSS severity8.7
High
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unbounded zlib decompression in Obsidian Forensics Unfurl before 2026.04 allows remote attackers to crash the service via a crafted URL. parse_compressed.py passes base64-decoded URL data to zlib.decompress() without limiting its output, allowing a small input to expand to gigabytes. No authentication or user interaction is required; deployment memory and URL-length limits determine whether resource exhaustion crashes the process.

The record

CVE
CVE-2026-40036
Published
Apr 8, 2026
Updated
Apr 8, 2026
Vendor
Obsidian Forensics
Product
Unfurl
Classifications
CWE-770, CWE-409, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <2026.04

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Obsidian Forensics · Unfurlversion=0 <2026.04

Published CVSS scores

7.5VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
CWE-409Improper Handling of Highly Compressed Data (Data Amplification)
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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