SimpleSAMLphp SAML2 library has incorrect signature verification for HTTP-Redirect binding
Priority HIGH 76CWE-347Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- None · High · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-347.
Summary
The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. Prior to versions 4.17.0 and 5.0.0-alpha.20, there is a signature confusion attack in the HTTPRedirect binding. An attacker with any signed SAMLResponse via the HTTP-Redirect binding can cause the application to accept an unsigned message. Versions 4.17.0 and 5.0.0-alpha.20 contain a fix for the issue.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00415 36th percentileScored 2026-11-07
Fix Fixed saml2 (simplesamlphp): 4.17.0, 5.0.0-alpha.20simplesamlphp/saml2 (Packagist): 4.17.0, 5.0.0-alpha.20+1 more product
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- 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 |
|---|---|---|---|---|---|
| simplesamlphp | saml2 | before 4.17.0; 5.0.0-alpha.1 to before 5.0.0-alpha.20 | 4.17.0, 5.0.0-alpha.20 | Patch available | CNA |
| — | simplesamlphp/saml2 (Packagist) | before 4.17.0 | 4.17.0 | Patch available | GHSA-46r4-f8gj-xg56 |
| — | simplesamlphp/saml2 (Packagist) | 5.0.0-alpha.1 to before 5.0.0-alpha.20 | 5.0.0-alpha.20 | Patch available | GHSA-46r4-f8gj-xg56 |
| — | simplesamlphp/saml2-legacy (Packagist) | before 4.17.0 | 4.17.0 | Patch available | GHSA-46r4-f8gj-xg56 |
- saml2 Vendorsimplesamlphp Affected before 4.17.0; 5.0.0-alpha.1 to before 5.0.0-alpha.20 Fixed in 4.17.0, 5.0.0-alpha.20 Patch available CNA
- simplesamlphp/saml2 (Packagist) Vendor— Affected before 4.17.0 Fixed in 4.17.0 Patch available GHSA-46r4-f8gj-xg56
- simplesamlphp/saml2 (Packagist) Vendor— Affected 5.0.0-alpha.1 to before 5.0.0-alpha.20 Fixed in 5.0.0-alpha.20 Patch available GHSA-46r4-f8gj-xg56
- simplesamlphp/saml2-legacy (Packagist) Vendor— Affected before 4.17.0 Fixed in 4.17.0 Patch available GHSA-46r4-f8gj-xg56
Remediation
- Fix · CNA saml2 (simplesamlphp) Fixed in 4.17.0, 5.0.0-alpha.20
- Fix · GHSA-46r4-f8gj-xg56 simplesamlphp/saml2 (Packagist) Fixed in 4.17.0 Advisory →
- Fix · GHSA-46r4-f8gj-xg56 simplesamlphp/saml2 (Packagist) Fixed in 5.0.0-alpha.20 Advisory →
- Fix · GHSA-46r4-f8gj-xg56 simplesamlphp/saml2-legacy (Packagist) Fixed in 4.17.0 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2025-27773
- 2026-10-03 Alias added: GHSA-46r4-f8gj-xg56
References
Other 6
- https://github.com/simplesamlphp/saml2/security/advisories/GHSA-46r4-f8gj-xg56
- https://github.com/simplesamlphp/saml2/commit/7867d6099dc7f31bed1ea10e5bea159c5623d2a0
- https://github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php#L104-L113
- https://github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php#L178-L217
- https://github.com/simplesamlphp/saml2
- https://lists.debian.org/debian-lts-announce/2025/05/msg00013.html
More simplesamlphp vulnerabilities
- TI-2026-25110 xml-security is Missing AES-GCM Authentication Tag Validation on Encrypted Nodes Allows for Unauthorized Decryption CVSS 3.1HIGH 8.2
- TI-2025-40522 SimpleSAMLphp-casserver has an Open Redirect vulnerability via logout CVSS 3.1MEDIUM 6.1
- TI-2018-04801 The sqlauth module in SimpleSAMLphp before 1.15.2 relies on the MySQL utf8 charset, which… CVSS 3.0CRITICAL 9.8
- TI-2024-35256 SimpleSAMLphp xml-common XXE vulnerability CVSS 4.0HIGH 8.8
- TI-2017-09530 The secureCompare method in lib/SimpleSAML/Utils/Crypto.php in SimpleSAMLphp 1.14.13 and… CVSS 3.0CRITICAL 9.8
- TI-2017-09535 SimpleSAMLphp 1.7.0 through 1.14.10 might allow attackers to obtain sensitive… CVSS 3.0CRITICAL 9.8
Sources
- CVE-2025-27773 · CVE Program
- CVE-2025-27773 · NVD
- FIRST EPSS
- GHSA-46r4-f8gj-xg56 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences