CVE catalog

CVE-2026-34827

Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as

[CVE catalog]

Severity
High · CVSS 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
Source
[NVD] · [CVE record]
EPSS
0.47% · Oct 25, 2026

Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name="..." using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

DistributionPackageReleaseVersionStatus
Debianruby-racksid3.2.7-1fixed
Debianruby-rackforky3.2.7-1fixed
Debianruby-racktrixie3.1.20-0+deb13u1vulnerable
Debianruby-racktrixie-security3.1.20-0+deb13u2fixed
Debianruby-rackbookworm2.2.22-0+deb12u1not affected
Debianruby-rackbookworm-security2.2.22-0+deb12u2not affected
Cperuby-rackNot reported2.2.7-1ubuntu0.7fixed
Cperuby-rackNot reportedNot reportedvulnerable
CperackNot reported3.1.21fixed
CperackNot reported3.2.6fixed
Ubunturuby-rackpro2.0.6-3vulnerable
Ubunturuby-rackpro2.0.7-2vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm1vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm2vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm3vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm4vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm5vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm6vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm7vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm8vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm9vulnerable
Ubunturuby-rackpro2.0.7-2ubuntu0.1+esm10vulnerable
Ubunturuby-rack22.042.1.4-3vulnerable
Ubunturuby-rack22.042.1.4-4vulnerable
Ubunturuby-rack22.042.1.4-5vulnerable
Ubunturuby-rack22.042.1.4-5ubuntu1vulnerable
Ubunturuby-rack22.042.1.4-5ubuntu1.1vulnerable
Ubunturuby-rack22.042.1.4-5ubuntu1.2vulnerable
Ubunturuby-rack24.042.2.4-3vulnerable
Ubunturuby-rack24.042.2.7-1vulnerable
Ubunturuby-rack24.042.2.7-1ubuntu0.1vulnerable
Ubunturuby-rack24.042.2.7-1ubuntu0.2vulnerable
Ubunturuby-rack24.042.2.7-1ubuntu0.3vulnerable
Ubunturuby-rack24.042.2.7-1ubuntu0.4vulnerable
Ubunturuby-rack24.042.2.7-1ubuntu0.5vulnerable
Ubunturuby-rack24.042.2.7-1ubuntu0.6vulnerable
Ubunturuby-rack24.042.2.7-1ubuntu0.7vulnerable
Ubunturuby-rack25.102.2.7-1.1vulnerable
Ubunturuby-rack25.103.1.16-0.1vulnerable
Ubunturuby-rack25.103.1.16-0.1ubuntu0.1vulnerable
Ubunturuby-rack25.103.1.16-0.1ubuntu0.2vulnerable
Ubunturuby-rack25.103.1.16-0.1ubuntu0.3fixed
Ubunturuby-rack26.043.1.16-0.1vulnerable
Ubunturuby-rack26.043.1.18-1vulnerable
Ubunturuby-rack26.043.1.18-1build1vulnerable
Ubunturuby-rack26.043.2.4-1ubuntu1vulnerable

Fixed-version evidence

DistributionPackageTypeReleaseFixed versionUrgencyOriginBugs
Debianruby-racksourcesid3.2.6-2not yet assignedNot reportedNot reported
Debianruby-racksourceforky3.2.6-2not yet assignedNot reportedNot reported
Debianruby-racksourcetrixie3.1.20-0+deb13u2not yet assignedNot reportedNot reported
Debianruby-racksourcebookwormNot affectedunimportantNot reportedNot reported
Cperuby-rackcpeNot reported2.2.7-1ubuntu0.7Not reportedNot reportedNot reported
CperackcpeNot reported3.1.21Not reportedNot reportedNot reported
CperackcpeNot reported3.2.6Not reportedNot reportedNot reported
Ubunturuby-rackdeb25.103.1.16-0.1ubuntu0.3Not reportedUBUNTU-CVE-2026-34827Not reported

OpenFactory catalog packages

[Debian 13 (Trixie)]

  • [ruby-rack]Affected
    Details (5)

    • 3.1.20-0+deb13u1 · all · trixie

      Affected · Fixed: 3.1.20-0+deb13u2

      nvd · ruby-rack · debian · 13

    • 3.1.20-0+deb13u1 · all · trixie

      Affected · Fixed: 3.1.20-0+deb13u2

      nvd · ruby-rack · debian · 13

    • 3.1.20-0+deb13u1 · all · trixie-security

      Affected · Fixed: 3.1.20-0+deb13u2

      nvd · ruby-rack · debian · 13

    • 3.1.20-0+deb13u1 · all · trixie-security · Historical version

      Affected · Fixed: 3.1.20-0+deb13u2

      nvd · ruby-rack · debian · 13

    • 3.1.20-0+deb13u2 · all · trixie-security

      Fixed · Fixed: 3.1.20-0+deb13u2

      nvd · ruby-rack · debian · 13

[Debian 12 (Bookworm)]

  • [ruby-rack]Not affected
    Details (4)

    • 2.2.22-0+deb12u1 · all · bookworm

      Not affected

      nvd · ruby-rack · debian · bookworm

    • 2.2.22-0+deb12u1 · all · bookworm

      Not affected

      nvd · ruby-rack · debian · bookworm

    • 2.2.22-0+deb12u2 · all · bookworm-security

      Not affected

      nvd · ruby-rack · debian · bookworm

    • 2.2.22-0+deb12u2 · all · bookworm-security

      Not affected

      nvd · ruby-rack · debian · bookworm

Observed:

References

[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX] · [Ubuntu Security Notices (USN)]