CVE-2026-40036 Details
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.
A denial-of-service vulnerability has been identified in Unfurl versions prior to 2026.04. The issue arises in the compressed data parser, which uses zlib.decompress() without a maximum output size limit. This flaw allows remote attackers to submit highly compressed payloads that expand significantly, leading to memory exhaustion and service crashes. The vulnerability can be exploited by sending base64-encoded zlib payloads through URL parameters to the /json/visjs endpoint.
Users are advised to update to Unfurl version 2026.04 or later, where this vulnerability has been fixed. The release notes for version 2026.04 can be found on the Unfurl GitHub Releases page.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Apr 11, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/obsidianforensics/unfurl/releases/tag/v2026.04 | [email protected] | Release Notes |
| https://github.com/obsidianforensics/unfurl/security/advisories/GHSA-h5qv-qjv4-pc5m | [email protected] | ExploitVendor Advisory |
| https://www.vulncheck.com/advisories/dfir-unfurl-denial-of-service-via-unbounded-zlib-decompression | [email protected] | Third Party Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-409 | Improper Handling of Highly Compressed Data (Data Amplification) | [email protected] |
| CWE-770 | Allocation of Resources Without Limits or Throttling | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| ryandfir unfurl | < 2026.04 |
CPE
Remediation
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Change History
6 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 24, 2026 | CVE Translated | [email protected] |
| Jul 14, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Apr 17, 2026 | Initial Analysis | [email protected] |
| Apr 8, 2026 | New CVE Received | [email protected] |