SimpleSAMLphp SAML2: Possible DoS via XPath Transform

published 2026-07-02 4 mo ago modified 2026-09-18 51 d ago also EUVD-2026-62505 , GHSA-5cjr-mxj5-wmrx

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.8%; EPSS 0.8% chance of exploitation in 30 days, percentile 56%
public exploits: 0; none known

The SimpleSAMLphp SAML2 library is a PHP library for SAML2 related functionality. In 4.19.2 and 4.20.2, the library permits attacker-controlled XPath transforms while processing XML signatures in specially crafted SAML messages. XPath evaluation can consume uncontrolled processing resources, allowing a remote unauthenticated attacker to deny service to any entity relying on SimpleSAMLphp or directly on the SAML2 library. The mitigation limits the number of transforms, permits only transform algorithms identified by the SAML 2.0 Core specification, and specifically rejects XPath transforms. This issue is fixed in versions 4.19.3 and 4.20.3.

Patch / fix

fixed in 3 links 2

packagist simplesamlphp/saml2 4.19.3, 4.20.3
packagist simplesamlphp/saml2-legacy 4.19.3, 4.20.3
simplesamlphp saml2 4.19.3, 4.20.3

github.com/simplesamlphp/saml2@0043033 commit
github.com/simplesamlphp/saml2@6695eb9 commit

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 2 mo ago (2026-08-19)

Exploit prediction

0.78% chance of exploitation in the next 30 days, higher than 56% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem	package	affected	fixed in
packagist	simplesamlphp/saml2	>=4.20.0, <4.20.3 <4.19.3	4.20.3 4.19.3
packagist	simplesamlphp/saml2-legacy	>=4.20.0, <4.20.3 <4.19.3	4.20.3 4.19.3

Affected products

simplesamlphp saml2

Classification

Weakness

CWE-400 Uncontrolled Resource Consumption

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary