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Fencer Vulns
medium 4.3

CVE-2020-8166 json

Ability to forge per-form CSRF tokens in Rails

published 2020-05-26 6 y ago modified 2026-06-17 4 mo ago also GHSA-jp5v-5gx4-jmj9 , EUVD-2020-0429

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 76%
public exploits
0
none known

Summary

A CSRF forgery vulnerability exists in rails < 5.2.5, rails < 6.0.4 that makes it possible for an attacker to, given a global CSRF token such as the one present in the authenticity_token meta tag, forge a per-form CSRF token.

Patch / fix

  • rubygems actionpack 5.2.4.3, 6.0.3.1
  • rubyonrails rails 5.2.4.3, 6.0.3.1
  • rails Debian 14, Debian 13, Debian 12 2:5.2.4.3+dfsg-1

debian advisories DEBIAN-CVE-2020-8166

  • tfm satellite capsule 6.9, satellite 6.9 6.1-4.el7sat
  • kobo satellite capsule 6.9, satellite 6.9 0.5.1-1.el7sat
  • pulp satellite capsule 6.9, satellite 6.9 2.21.5-2.el7sat
  • gofer satellite capsule 6.9, satellite 6.9 2.12.5-7.el7sat
  • future satellite capsule 6.9, satellite 6.9 0.16.0-11.el7sat
  • ostree satellite capsule 6.9, satellite 6.9 2017.1-2.atomic.el7
  • foreman satellite capsule 6.9, satellite 6.9 2.3.1.20-1.el7sat
  • katello satellite capsule 6.9, satellite 6.9 3.18.1-3.el7sat

red hat advisories RHSA-2021:1313

  • rubygem-actionpack-5_1 SLE High Availability Extension 15 SP5, SLE High Availability Extension 15 SP4, SLE High Availability Extension 15 SP3 +4 more 5.1.4-150000.3.29.1
  • rmt-server SLE Module for Server Applications 15 SP1, SLE Module for Public Cloud 15 SP1 2.6.5-3.18.1
  • rmt-server SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 2.6.5-3.34.1
  • rmt-server SLE Module for Server Applications 15 SP2, SLE Module for Public Cloud 15 SP2 2.6.5-3.3.1

suse advisories SUSE-SU-2024:0103-1SUSE-SU-2020:3160-1SUSE-SU-2020:3147-1SUSE-SU-2020:3036-1

  • rmt-server openSUSE Tumbleweed 2.6.13-1.1
  • rubygem-actionpack-6.0 openSUSE Tumbleweed 6.0.4.4-1.1
  • rmt-server openSUSE Leap 15.1 2.6.5-lp151.2.18.2
  • rmt-server openSUSE Leap 15.2 2.6.5-lp152.2.3.1

opensuse advisories openSUSE-SU-2024:10589-1openSUSE-SU-2024:11821-1openSUSE-SU-2020:2000-1openSUSE-SU-2020:1993-1

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-2020-8166 updated cvss 0.0

rubygem-actionpack: ability to forge per-form CSRF tokens given a global CSRF token

  • Red Hat CloudForms Management Engine 5 cfme-gemset
    affected: no fix planned “Will not fix”
  • Red Hat Satellite 6.9 tfm 6.1-4.el7sat, kobo 0.5.1-1.el7sat, pulp 2.21.5-2.el7sat, gofer 2.12.5-7.el7sat, libsolv 0.7.12-2.el7pc, receptor 0.6.3-1.el7ar, +646 more Red Hat Satellite Capsule 6.9 tfm 6.1-4.el7sat, kobo 0.5.1-1.el7sat, pulp 2.21.5-2.el7sat, gofer 2.12.5-7.el7sat, libsolv 0.7.12-2.el7pc, future 0.16.0-11.el7sat, +254 more
    fixed: vendor fix RHSA-2021:1313
  • Red Hat CloudForms Management Engine 5 cfme-amazon-smartstate
    not affected: vulnerable code not present

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

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

1.67% chance of exploitation in the next 30 days, higher than 76% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • hackerone.com https://hackerone.com/reports/732415 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N
GitHub 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
rubygems actionpack
>=5.0.0, <5.2.4.3
>=6.0.0, <6.0.3.1
5.2.4.3
6.0.3.1

Affected products

  • n/a https://github.com/rails/rails

Classification

Weakness
  • CWE-352 Cross-Site Request Forgery
Technology feeds

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.