CVE-2026-40036: Unfurl before 2026.04 contains an unbounded zlib decompression vulnerability in parse_compressed.py that allow

Q: How do I fix CVE-2026-40036?

unfurl: upgrade to 2026.04. Exact commands for each OS are on this page.

Q: Is CVE-2026-40036 being exploited?

CVE-2026-40036 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-40036 affect?

CVE-2026-40036 affects unfurl. Severity is high (CVSS 7.5). 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/vis

Q: How urgent is CVE-2026-40036?

Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-40036 is a high-severity flaw (CVSS 7.5) affecting unfurl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 57%)
CISA exploited list	No
Weakness	CWE-409, CWE-770
Published	2026-04-08
Last modified	2026-10-08

Publisher (CNA): VulnCheck · Vendor: ryandfir

Last updated 2026-10-08 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-08 22:16 UTCPublished CVE record published
2026-10-08 16:17 UTCUpdated Record last modified

ryandfir unfurl UPGRADE

Affected: < 2026.04

Fixed in: 2026.04

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy unfurl || rpm -q unfurl || unfurl --version

2. UPGRADE to 2026.04 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade unfurl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade unfurl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40036?

unfurl: upgrade to 2026.04. Exact commands for each OS are on this page.

Is CVE-2026-40036 being exploited?

CVE-2026-40036 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40036 affect?

CVE-2026-40036 affects unfurl. Severity is high (CVSS 7.5). 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/vis

How urgent is CVE-2026-40036?

Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

zlib vulnerabilities

Related CVEs

CVE-2026-40035 CRITICAL 9.1 UPGRADE Unfurl through 2025.08 contains an improper input validation vulnerability in config parsing that enables Flas

References

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