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Fencer Vulns
high 7.5

CVE-2020-7663 json

Regular Expression Denial of Service in websocket-extensions (RubyGem)

published 2020-06-02 6 y ago modified 2026-07-08 4 mo ago also GHSA-g6wq-qcwm-j5g2 , EUVD-2020-0487

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.6%
EPSS 4.6% chance of exploitation in 30 days, percentile 91%
public exploits
0
none known

Summary

websocket-extensions ruby module prior to 0.1.5 allows Denial of Service (DoS) via Regex Backtracking. The extension parser may take quadratic time when parsing a header containing an unclosed string parameter value whose content is a repeating two-byte sequence of a backslash and some other character. This could be abused by an attacker to conduct Regex Denial Of Service (ReDoS) on a single-threaded server by providing a malicious payload with the Sec-WebSocket-Extensions header.

Patch / fix

  • rubygems websocket-extensions 0.1.5
  • websocket-extensions_project websocket-extensions 0.1.5
  • ruby-websocket-extensions Debian 14, Debian 13, Debian 12 0.1.5-1

debian advisories DEBIAN-CVE-2020-7663

  • ruby-websocket-extensions Ubuntu 16.04 LTS 0.1.2-1+deb9u1build0.16.04.1
  • ruby-websocket-extensions Ubuntu 18.04 LTS 0.1.2-1+deb9u1build0.18.04.1
  • ruby-websocket-extensions Ubuntu 20.04 LTS 0.1.2-1+deb9u1build0.20.04.1

ubuntu advisories UBUNTU-CVE-2020-7663

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • tfm satellite capsule 6.8, satellite 6.8 6.1-1.el7sat
  • kobo satellite capsule 6.8, satellite 6.8 0.5.1-1.el7sat
  • pulp satellite capsule 6.8, satellite 6.8 2.21.3-1.el7sat
  • gofer satellite capsule 6.8, satellite 6.8 2.12.5-7.el7sat
  • future satellite capsule 6.8, satellite 6.8 0.16.0-11.el7sat
  • ostree satellite capsule 6.8, satellite 6.8 2017.1-2.atomic.el7
  • foreman satellite capsule 6.8, satellite 6.8 2.1.2.19-1.el7sat
  • katello satellite capsule 6.8, satellite 6.8 3.16.0-1.el7sat

red hat advisories RHSA-2020:4366

  • rubygem-websocket-extensions SLE High Availability Extension 15 SP4, SLE High Availability Extension 15 SP3, SLE High Availability Extension 15 SP2 +2 more 0.1.3-150000.3.4.1

suse advisories SUSE-SU-2023:0127-1

  • rubygem-websocket-extensions openSUSE Tumbleweed 0.1.5-1.24
  • rubygem-websocket-extensions openSUSE Tumbleweed 0.1.5-1.22
  • rubygem-websocket-extensions openSUSE Tumbleweed 0.1.5-1.20
  • ruby3.2-rubygem-websocket-extensions openSUSE Tumbleweed 0.1.5-1.16

opensuse advisories openSUSE-SU-2026:10368-1openSUSE-SU-2025:15130-1openSUSE-SU-2024:14180-1openSUSE-SU-2024:13173-1

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-2020-7663 updated cvss 0.0

rubygem-websocket-extensions: ReDoS vulnerability in Sec-WebSocket-Extensions parser

  • Red Hat CloudForms Management Engine 5 cfme-gemset
    affected: no fix planned “Out of support scope”
  • Red Hat Satellite 6.8 tfm 6.1-1.el7sat, kobo 0.5.1-1.el7sat, pulp 2.21.3-1.el7sat, gofer 2.12.5-7.el7sat, receptor 0.6.3-1.el7ar, future 0.16.0-11.el7sat, +488 more Red Hat Satellite Capsule 6.8 tfm 6.1-1.el7sat, kobo 0.5.1-1.el7sat, pulp 2.21.3-1.el7sat, gofer 2.12.5-7.el7sat, future 0.16.0-11.el7sat, katello 3.16.0-1.el7sat, +232 more
    fixed: vendor fix RHSA-2020:4366

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

Exploit prediction

4.64% chance of exploitation in the next 30 days, higher than 91% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • snyk.io https://snyk.io/vuln/SNYK-RUBY-WEBSOCKETEXTENSIONS-570830 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Affected packages

ecosystem package affected fixed in
rubygems websocket-extensions
<0.1.5
0.1.5

Affected products

  • n/a websocket-extensions (ruby)

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

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.