CVE-2026-49289: Simplesamlphp/saml2 Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-5cjr-mxj5-wmrx
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CVSS 7.5
CWE-400
Published
Advisory Summary

CVE-2026-49289 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Simplesamlphp/saml2 libraries in the Packagist ecosystem. The issue involves simplesamlphp has possible dos via xpath transform. Remediation is available by upgrading affected packages to version 4.20.3, 4.19.3.

CVE-2026-49289 at a Glance

CVE Identifier CVE-2026-49289
GHSA Identifier GHSA-5cjr-mxj5-wmrx
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Simplesamlphp/saml2
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-49289

To remediate this vulnerability, upgrade all affected Simplesamlphp/saml2 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

simplesamlphp/saml2 fixed: 4.20.3 
Upgrade simplesamlphp/saml2 to 4.20.3
simplesamlphp/saml2-legacy fixed: 4.20.3 
Upgrade simplesamlphp/saml2-legacy to 4.20.3
simplesamlphp/saml2 fixed: 4.19.3 
Upgrade simplesamlphp/saml2 to 4.19.3
simplesamlphp/saml2-legacy fixed: 4.19.3 
Upgrade simplesamlphp/saml2-legacy to 4.19.3
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for simplesamlphp/saml2

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-49289, inspect your project dependencies for Simplesamlphp/saml2:

inspect dependencies for simplesamlphp/saml2

Analyze the terminal output to locate any version of Simplesamlphp/saml2 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.20.3), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Simplesamlphp/saml2, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## Summary This library turned out to be vulnerable to Denial-of-Service attacks using XPath transforms. A mitigation has been put in place to restrict the number of transforms and to restrict transforms to only the transform-algorithms mentioned in the SAML 2.0 Core Specifications (and specifically refuse XPath transforms). ## Impact An attacker is able to send specially crafted messages to any entity relying on SimpleSAMLphp (or directly on this SAML2-library) to be able to perform a Denial-of-Service attack.

CVE-2026-49289 Affected Simplesamlphp/saml2 Versions

4 component(s)
Fixed Versions:
4.20.34.19.3
Product / Package Ecosystem Affected Versions Fixed Version
simplesamlphp/saml2
 Packagist
≥ 4.20.0
< 4.20.3
4.20.3
simplesamlphp/saml2-legacy
 Packagist
≥ 4.20.0
< 4.20.3
4.20.3
simplesamlphp/saml2
 Packagist
< 4.19.3
4.19.3
simplesamlphp/saml2-legacy
 Packagist
< 4.19.3
4.19.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/simplesamlphp/saml2/security/advisories/GHSA-5cjr-mxj5-wmrx
Simplesamlphp/saml2 Source Repository REPOSITORY
https://github.com/simplesamlphp/saml2

Frequently Asked Questions

What is CVE-2026-49289?
CVE-2026-49289 is a security vulnerability in Simplesamlphp/saml2 involving SimpleSAMLphp has Possible DoS via XPath Transform under CWE-400: Uncontrolled Resource Consumption.
Which Simplesamlphp/saml2 versions are affected?
Affected versions include releases prior to 4.20.3, 4.19.3 across affected packages: simplesamlphp/saml2, simplesamlphp/saml2-legacy.
What version fixes CVE-2026-49289?
Upgrading to 4.20.3, 4.19.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is simplesamlphp/saml2 affected?
Yes, simplesamlphp/saml2 is affected in releases prior to 4.20.3, 4.19.3. Upgrade your dependency to 4.20.3, 4.19.3 or later.
Is simplesamlphp/saml2-legacy affected?
Yes, simplesamlphp/saml2-legacy is affected in releases prior to 4.20.3, 4.19.3. Upgrade your dependency to 4.20.3, 4.19.3 or later.
What is the CVSS score of CVE-2026-49289?
CVE-2026-49289 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-49289?
CVE-2026-49289 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check Packagist dependencies for CVE-2026-49289?
Run the dependency tree command: 'inspect dependencies for simplesamlphp/saml2'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-5cjr-mxj5-wmrx",
  "modified" : "2026-08-05T12:44:43Z",
  "published" : "2026-07-02T20:27:23Z",
  "aliases" : [ "CVE-2026-49289" ],
  "summary" : "SimpleSAMLphp has Possible DoS via XPath Transform",
  "details" : "## Summary\n\nThis library turned out to be vulnerable to Denial-of-Service attacks using XPath transforms. A mitigation has been put in place to restrict the number of transforms and to restrict transforms to only the transform-algorithms mentioned in the SAML 2.0 Core Specifications (and specifically refuse XPath transforms).\n\n## Impact\n\nAn attacker is able to send specially crafted messages to any entity relying on SimpleSAMLphp (or directly on this SAML2-library) to be able to perform a Denial-of-Service attack.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "simplesamlphp/saml2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.20.0"
      }, {
        "fixed" : "4.20.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.20.2"
    }
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "simplesamlphp/saml2-legacy"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.20.0"
      }, {
        "fixed" : "4.20.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.20.2"
    }
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "simplesamlphp/saml2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.19.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.19.2"
    }
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "simplesamlphp/saml2-legacy"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.19.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.19.2"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/simplesamlphp/saml2/security/advisories/GHSA-5cjr-mxj5-wmrx"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/simplesamlphp/saml2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-02T20:27:23Z",
    "nvd_published_at" : null
  }
}