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CVE-2025-66567

31
FAUCET Score

CVE-2025-66567 is an authentication bypass vulnerability affecting ruby-saml versions up to and including 1.12.4, stemming from an incomplete fix for a prior CVE. It allows attackers to perform a Signature Wrapping attack due to differing XML parsing behaviors between REXML and Nokogiri, impacting the client-side implementation of SAML authorization. This critical vulnerability, with a CVSS score of 9.1, has a low attack complexity and can lead to high confidentiality and integrity impacts. While there is no known exploit code or active exploitation, the vulnerability has garnered significant community discussion and media coverage, indicating a high level of concern.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.18.0CPE matchmatch criteria
cpe:2.3:a:onelogin:ruby-saml:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

9.3CRITICAL

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
HIGH
VS Integrity
HIGH
VS Availability
NONE
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.39%
Probability of exploitation in next 30 days
EPSS Percentile
31.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0039 is in the 9th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
rubygemspatch availablevia ghsa
Product: ruby-samlFixed in: 1.18.0

Vendor Advisories (1)

rubygemsGHSA-9v8j-x534-2fx3critical

Ruby-saml has a SAML authentication bypass due to namespace handling (parser differential)

Dec 8, 2025

References

github.com / advisories/GHSA-754f-8gm6-c4r2
Not Applicable
github.com / SAML-Toolkits/ruby-saml/commit/e9c1cdbd0f9afa467b585de279db0cbd0fb8ae97
Patch
github.com / SAML-Toolkits/ruby-saml/security/advisories/GHSA-9v8j-x534-2fx3
Vendor Advisory