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Fencer Vulns
high 7.8

CVE-2008-3656 in the critical feed json

Algorithmic complexity vulnerability in the WEBrick::HTTPUtils.split_header_value function in WEBrick::HTTP::DefaultFileHandler in WEBrick…

published 2008-08-13 18 y ago modified 2026-06-16 4 mo ago also EUVD-2008-3642

cvss
7.8
version 2.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
70.2%
EPSS 70.2% chance of exploitation in 30 days, percentile 99.3%
public exploits
2
Metasploit, Exploit-DB

Summary

Algorithmic complexity vulnerability in the WEBrick::HTTPUtils.split_header_value function in WEBrick::HTTP::DefaultFileHandler in WEBrick in Ruby 1.8.5 and earlier, 1.8.6 through 1.8.6-p286, 1.8.7 through 1.8.7-p71, and 1.9 through r18423 allows context-dependent attackers to cause a denial of service (CPU consumption) via a crafted HTTP request that is processed by a backtracking regular expression.

Patch / fix

  • ruby4.0 hummingbird 1 4.0.0-33.3.hum1
  • ruby4.0-libs hummingbird 1 4.0.0-33.3.hum1
  • ruby4.0-bundled-gems hummingbird 1 4.0.0-33.3.hum1
  • ruby4.0-default-gems hummingbird 1 4.0.0-33.3.hum1
  • ruby3.3 hummingbird 1 3.3.10-23.1.hum1
  • ruby3.3-libs hummingbird 1 3.3.10-23.1.hum1
  • ruby3.3-bundled-gems hummingbird 1 3.3.10-23.1.hum1
  • ruby3.3-default-gems hummingbird 1 3.3.10-23.1.hum1

red hat advisories RHSA-2026:8838RHSA-2026:7305RHSA-2026:7307RHSA-2008:0897

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2008-3656 updated

ruby: WEBrick DoS vulnerability (CPU consumption)

  • Red Hat Enterprise Linux (v. 5 server) ruby 1.8.5-5.el5_2.5, ruby-ri 1.8.5-5.el5_2.5, ruby-irb 1.8.5-5.el5_2.5, ruby-libs 1.8.5-5.el5_2.5, ruby-mode 1.8.5-5.el5_2.5, ruby-rdoc 1.8.5-5.el5_2.5, +1 more Red Hat Enterprise Linux AS version 4 irb 1.8.1-7.el4_7.1, ruby 1.8.1-7.el4_7.1, ruby-libs 1.8.1-7.el4_7.1, ruby-mode 1.8.1-7.el4_7.1, ruby-tcltk 1.8.1-7.el4_7.1 Red Hat Enterprise Linux Desktop (v. 5 client) ruby 1.8.5-5.el5_2.5, ruby-ri 1.8.5-5.el5_2.5, ruby-irb 1.8.5-5.el5_2.5, ruby-libs 1.8.5-5.el5_2.5, ruby-mode 1.8.5-5.el5_2.5, ruby-rdoc 1.8.5-5.el5_2.5, +1 more Red Hat Enterprise Linux Desktop version 4 irb 1.8.1-7.el4_7.1, ruby 1.8.1-7.el4_7.1, ruby-libs 1.8.1-7.el4_7.1, ruby-mode 1.8.1-7.el4_7.1, ruby-tcltk 1.8.1-7.el4_7.1 Red Hat Enterprise Linux Desktop Workstation (v. 5 client) ruby 1.8.5-5.el5_2.5, ruby-ri 1.8.5-5.el5_2.5, ruby-irb 1.8.5-5.el5_2.5, ruby-libs 1.8.5-5.el5_2.5, ruby-mode 1.8.5-5.el5_2.5, ruby-rdoc 1.8.5-5.el5_2.5, +1 more Red Hat Enterprise Linux ES version 4 irb 1.8.1-7.el4_7.1, ruby 1.8.1-7.el4_7.1, ruby-libs 1.8.1-7.el4_7.1, ruby-mode 1.8.1-7.el4_7.1, ruby-tcltk 1.8.1-7.el4_7.1
    +1 more products
    Red Hat Enterprise Linux WS version 4 irb 1.8.1-7.el4_7.1, ruby 1.8.1-7.el4_7.1, ruby-libs 1.8.1-7.el4_7.1, ruby-mode 1.8.1-7.el4_7.1, ruby-tcltk 1.8.1-7.el4_7.1
    fixed: vendor fix RHSA-2008:0897
  • Red Hat Hardened Images ruby3.4 3.4.8-31.1.hum1, ruby4.0 4.0.0-33.3.hum1, ruby3.3 3.3.10-23.1.hum1, ruby3.4-default-gems 3.4.8-31.1.hum1, ruby4.0-default-gems 4.0.0-33.3.hum1, ruby3.3-default-gems 3.3.10-23.1.hum1
    fixed: vendor fix RHSA-2026:7305

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Timeline

  1. First public exploit (Metasploit auxiliary/dos/http/webrick_regex)
  2. Published

Exploit prediction

70.20% chance of exploitation in the next 30 days, higher than 99.3% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Metasploit auxiliary/dos/http/webrick_regex Ruby WEBrick::HTTP::DefaultFileHandler DoS metasploit auxiliary, normal rank, 2008-08-08
  • EDB-32222 Ruby 1.9 - 'WEBrick::HTTP::DefaultFileHandler' Crafted HTTP Request Denial of Service dos, 2008-08-11
  • ruby-lang.org http://www.ruby-lang.org/en/news/2008/08/08/multiple-vulnerabilities-in-ruby/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 2.0 7.8 AV:N/AC:L/Au:N/C:N/I:N/A:C

Classification

Weakness
  • CWE-399 Resource Management Errors

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.