Ruby SAML DOS vulnerability with large SAML response
Priority LOW 37CWE-400Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-400.
Summary
The Ruby SAML library is for implementing the client side of a SAML authorization. In versions 1.18.0 and below, a denial-of-service vulnerability exists in ruby-saml even with the message_max_bytesize setting configured. The vulnerability occurs because the SAML response is validated for Base64 format prior to checking the message size, leading to potential resource exhaustion. This is fixed in version 1.18.1.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0046 40th percentileScored 2026-11-07
Fix Fixed ruby-saml (SAML-Toolkits): 1.18.1ruby-saml (RubyGems): 1.18.1
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| SAML-Toolkits | ruby-saml | before 1.18.1 | 1.18.1 | Patch available | CNA |
| — | ruby-saml (RubyGems) | before 1.18.1 | 1.18.1 | Patch available | GHSA-rrqh-93c8-j966 |
- ruby-saml VendorSAML-Toolkits Affected before 1.18.1 Fixed in 1.18.1 Patch available CNA
- ruby-saml (RubyGems) Vendor— Affected before 1.18.1 Fixed in 1.18.1 Patch available GHSA-rrqh-93c8-j966
Remediation
- Fix · CNA ruby-saml (SAML-Toolkits) Fixed in 1.18.1
- Fix · GHSA-rrqh-93c8-j966 ruby-saml (RubyGems) Fixed in 1.18.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2025-54572
- 2026-10-03 Alias added: GHSA-rrqh-93c8-j966
References
Other 7
- https://github.com/SAML-Toolkits/ruby-saml/security/advisories/GHSA-rrqh-93c8-j966
- https://github.com/SAML-Toolkits/ruby-saml/pull/770
- https://github.com/SAML-Toolkits/ruby-saml/commit/38ef5dd1ce17514e202431f569c4f5633e6c2709
- https://github.com/SAML-Toolkits/ruby-saml/releases/tag/v1.18.1
- https://github.com/SAML-Toolkits/ruby-saml
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/ruby-saml/CVE-2025-54572.yml
- https://lists.debian.org/debian-lts-announce/2025/09/msg00001.html
More SAML-Toolkits vulnerabilities
- TI-2025-18946 Ruby SAML vulnerable to SAML authentication bypass due to namespace handling (parser differential) CVSS 4.0CRITICAL 9.3
- TI-2024-30458 The Ruby SAML library vulnerable to a SAML authentication bypass via Incorrect XPath selector CVSS 3.1CRITICAL 10.0
- TI-2025-18945 ruby-saml vulnerable to SAML authentication bypass due to DOCTYPE handling (parser differential) CVSS 4.0CRITICAL 9.3
- TI-2015-08083 xml_security.rb in the ruby-saml gem before 1.0.0 for Ruby allows XPath injection and… CVSS 3.1CRITICAL 9.8
- TI-2017-08452 Multiple SAML libraries may allow authentication bypass via incorrect XML canonicalization and DOM traversal CVSS 3.0CRITICAL 9.8
- TI-2025-40979 ruby-saml Libxml2 Canonicalization errors can bypass Digest/Signature validation CVSS 4.0CRITICAL 9.3
Sources
- CVE-2025-54572 · CVE Program
- CVE-2025-54572 · NVD
- FIRST EPSS
- GHSA-rrqh-93c8-j966 · GitHub Advisory Database · CC BY 4.0
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