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Fencer Vulns
critical 9.8

CVE-2019-10842 json

Bootstrap-sass contains code execution backdoor

published 2019-04-04 7 y ago modified 2026-06-17 4 mo ago also GHSA-vqqv-v9m2-48p2 , EUVD-2019-0438

cvss
9.8
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.9%
EPSS 4.9% chance of exploitation in 30 days, percentile 92%
public exploits
0
none known

Summary

Arbitrary code execution (via backdoor code) was discovered in bootstrap-sass 3.2.0.3, when downloaded from rubygems.org. An unauthenticated attacker can craft the ___cfduid cookie value with base64 arbitrary code to be executed via eval(), which can be leveraged to execute arbitrary code on the target system. Note that there are three underscore characters in the cookie name. This is unrelated to the __cfduid cookie that is legitimately used by Cloudflare.

Patch / fix

  • rubygems bootstrap-sass 3.2.0.4

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-2019-10842 updated cvss 9.8

rubygem-bootstrap-sass: backdoor code allows arbitrary code execution when downloaded from rubygems.org

  • Red Hat CloudForms Management Engine 5 cfme-gemset
    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

Exploit prediction

4.92% chance of exploitation in the next 30 days, higher than 92% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • snyk.io https://snyk.io/blog/malicious-remote-code-execution-backdoor-discovered-in-the-popular-bootstrap-sass-ruby-gem/ referenced PoC, tagged "exploit" by a source, unverified
  • snyk.io https://snyk.io/vuln/SNYK-RUBY-BOOTSTRAPSASS-174093 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.0 9.8 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 10.0 AV:N/AC:L/Au:N/C:C/I:C/A:C
GitHub 3.0 9.8 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
rubygems bootstrap-sass
>=3.2.0.3, <3.2.0.4
3.2.0.4

Classification

Weakness
  • CWE-94 Improper Control of Generation of Code

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.