Is CVE-2026-34230 in the CISA KEV catalog?

No. CVE-2026-34230 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-34230?

CVE-2026-34230 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2026-34230?

CVE-2026-34230 has an EPSS score of 0.43% (35th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-34230?

Upgrade ruby-rack on debian unstable to 3.2.6-2 or later. Fixes are available for 5 affected products.

CVE & CISA-KEV Catalog

CVE-2026-34230

MEDIUM

5.3

CVSS v3

NVD

Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Utils.select_best_encoding processes Accept-Encoding values with quadratic time complexity when the header contains many wildcard (*) entries. Because this method is used by Rack::Deflater to choose a response encoding, an unauthenticated attacker can send a single request with a crafted Accept-Encoding header and cause disproportionate CPU consumption on the compression middleware path. This results in a denial of service condition for applications using Rack::Deflater. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

CWE-400Resource Exhaustion CWE-407

How to fix

Remediation Available

ruby-rackDebian

Fixed in:3.2.6-2CVE-2026-34230

librack-rubyUbuntu

Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1

librack-ruby1.8Ubuntu

Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1

librack-ruby1.9.1Ubuntu

Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1

ruby-rackUbuntu

Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1

Fixed in:1.6.4-3ubuntu0.2+esm10USN-8182-1

Fixed in:1.6.4-4ubuntu0.2+esm10USN-8182-1

Fixed in:2.0.7-2ubuntu0.1+esm10USN-8182-1

Fixed in:2.1.4-5ubuntu1.2+esm3USN-8182-1

Fixed in:2.2.7-1ubuntu0.7USN-8182-1

Fixed in:3.1.16-0.1ubuntu0.3USN-8182-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityLow

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Exploit Intelligence

0.43%probability of exploitation in 30 days

35thpercentile

Low risk: more likely to be exploited than 35% of all known CVEs.

References

Vendor Advisory1

github.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-16.