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CVE-2026-34829

28
FAUCET Score

CVE-2026-34829 affects Rack, a modular Ruby web server interface, specifically versions prior to 2.2.23, 3.1.21, and 3.2.6. The vulnerability allows an unauthenticated attacker to trigger a denial of service by sending multipart/form-data requests without a Content-Length header, enabling unbounded streaming of data directly to disk. This high-severity issue (CVSS 7.5, AV:N/AC:L/A:H) has low attack complexity and can lead to complete disk exhaustion on affected systems. There is currently no evidence of active exploitation, nor are public exploit modules available in common repositories like Metasploit or ExploitDB, with minimal community discussion observed.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.2.23CPE matchmatch criteria
cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
>= 3.0.0, < 3.1.21CPE matchmatch criteria
cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
>= 3.2.0, < 3.2.6CPE matchmatch criteria
cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.37%
Probability of exploitation in next 30 days
EPSS Percentile
29.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0037 is in the 10th percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (11)

rubygemspatch availablevia ghsa
Product: rackFixed in: 3.1.21
rubygemspatch availablevia ghsa
Product: rackFixed in: 3.2.6
rubygemspatch availablevia ghsa
Product: rackFixed in: 2.2.23
ubuntupatch availablevia ubuntu_usn
Product: ruby-rack (jammy)Fixed in: 2.1.4-5ubuntu1.2+esm3
ubuntupatch availablevia ubuntu_usn
Product: ruby-rack (noble)Fixed in: 2.2.7-1ubuntu0.7
ubuntupatch availablevia ubuntu_usn
Product: ruby-rack (questing)Fixed in: 3.1.16-0.1ubuntu0.3
ubuntupatch availablevia ubuntu_usn
Product: ruby-rack (trusty)Fixed in: 1.5.2-3+deb8u3ubuntu1~esm11
ubuntupatch availablevia ubuntu_usn
Product: ruby-rack (xenial)Fixed in: 1.6.4-3ubuntu0.2+esm10
ubuntupatch availablevia ubuntu_usn
Product: ruby-rack (bionic)Fixed in: 1.6.4-4ubuntu0.2+esm10
ubuntupatch availablevia ubuntu_usn
Product: ruby-rack (focal)Fixed in: 2.0.7-2ubuntu0.1+esm10
github_advisoryvendor investigatingvia nvd_reference
View patch

Vendor Advisories (2)

ubuntuUSN-8182-1

Rack vulnerabilities

Apr 17, 2026
rubygemsGHSA-8vqr-qjwx-82mwhigh

Rack's multipart parsing without Content-Length header allows unbounded chunked file uploads

Apr 2, 2026

References

access.redhat.com / security/cve/CVE-2026-34829
bugzilla.redhat.com / show_bug.cgi
security.access.redhat.com / data/csaf/v2/vex/2026/cve-2026-34829.json
github.com / rack/rack/security/advisories/GHSA-8vqr-qjwx-82mw
Vendor Advisory