Authentication bypass (Signature Wrapping) in ruby-saml (ReXML vs Nokogiri parser discrepancy)
CVE-2025-66567 is an authentication bypass in the ruby-saml library (client-side SAML implementation) affecting versions up to and including 1.12.4. The issue stems from an incomplete fix for CVE-2025-25292 and a fragile multi-parser design: ReXML and Nokogiri/libxml2 parse the same XML into different document structures. ruby-saml uses these parsers for different parts of XML Signature processing (e.g., locating/reading signature-related values vs. processing/transforms/canonicalization of signed content), enabling an attacker to craft a SAML Response that passes signature verification while the application consumes an attacker-controlled Assertion. This is a Signature Wrapping-style attack enabled by parser inconsistencies.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
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Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
11 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Ruby-SAML vulnerability (pre-1.18.0, including 1.12.4) tied to the paper’s described SAML signature-validation bypass techniques (parser inconsistencies / canonicalization-related bypasses).
A critical authentication bypass vulnerability in the ruby-saml library due to improper namespace handling and parser differentials, allowing attackers to execute Signature Wrapping attacks and bypass SAML authentication.
A critical authentication bypass vulnerability in the Ruby SAML library.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.