CVE catalog

CVE-2026-34831

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Files#fail sets the Content-Length response header using String#size instead of String#bytesize. When th

[CVE catalog]

Severity
Medium · CVSS 4.8CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Published
Source
[NVD] · [CVE record]
EPSS
0.15% · Oct 25, 2026

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Files#fail sets the Content-Length response header using String#size instead of String#bytesize. When the response body contains multibyte UTF-8 characters, the declared Content-Length is smaller than the number of bytes actually sent on the wire. Because Rack::Files reflects the requested path in 404 responses, an attacker can trigger this mismatch by requesting a non-existent path containing percent-encoded UTF-8 characters. This results in incorrect HTTP response framing and may cause response desynchronization in deployments that rely on the incorrect Content-Length value. This issue has been patched in versions 2.2.23, 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+deb12u1vulnerable
Debianruby-rackbookworm-security2.2.22-0+deb12u2fixed
Cperuby-rackNot reported2.2.7-1ubuntu0.7fixed
Cperuby-rackNot reportedNot reportedvulnerable
CperackNot reported2.2.23fixed
CperackNot reported3.1.21fixed
CperackNot reported3.2.6fixed
Ubunturuby-rackpro2.1.4-3vulnerable
Ubunturuby-rackpro2.1.4-4vulnerable
Ubunturuby-rackpro2.1.4-5vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1+esm2vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1+esm3vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1+esm4vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1+esm5vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1.1vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1.1+esm1vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1.1+esm2vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1.2vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1.2+esm1vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1.2+esm2vulnerable
Ubunturuby-rackpro2.1.4-5ubuntu1.2+esm3fixed
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-rack24.042.2.7-1ubuntu0.7fixed
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-racksourcebookworm2.2.22-0+deb12u2not yet assignedNot reportedNot reported
Cperuby-rackcpeNot reported2.2.7-1ubuntu0.7Not reportedNot reportedNot reported
CperackcpeNot reported2.2.23Not reportedNot reportedNot reported
CperackcpeNot reported3.1.21Not reportedNot reportedNot reported
CperackcpeNot reported3.2.6Not reportedNot reportedNot reported
Ubunturuby-rackdebpro2.1.4-5ubuntu1.2+esm3Not reportedUBUNTU-CVE-2026-34831Not reported
Ubunturuby-rackdeb24.042.2.7-1ubuntu0.7Not reportedUBUNTU-CVE-2026-34831Not reported
Ubunturuby-rackdeb25.103.1.16-0.1ubuntu0.3Not reportedUBUNTU-CVE-2026-34831Not reported

OpenFactory catalog packages

[Debian 12 (Bookworm)]

  • [ruby-rack]Affected
    Details (4)

    • 2.2.22-0+deb12u1 · all · bookworm

      Affected · Fixed: 2.2.22-0+deb12u2

      nvd · ruby-rack · debian · bookworm; nvd · ruby-rack · debian · 12

    • 2.2.22-0+deb12u1 · all · bookworm

      Affected · Fixed: 2.2.22-0+deb12u2

      nvd · ruby-rack · debian · bookworm; nvd · ruby-rack · debian · 12

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

      Fixed · Fixed: 2.2.22-0+deb12u2

      nvd · ruby-rack · debian · bookworm; nvd · ruby-rack · debian · 12

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

      Fixed · Fixed: 2.2.22-0+deb12u2

      nvd · ruby-rack · debian · bookworm; nvd · ruby-rack · debian · 12

[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

Observed:

References

[CERT-Bund public advisories] · [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)]