CVE-2026-49284: SimpleSAMLphp SP accepts a response from an unexpected IdP when unsigned `Response/InResponseTo` is combined with a signed assertion lacking `SubjectConfirmationData/InResponseTo`

high Affects simplesamlphp/simplesamlphp. Feed 2026.10.29.1, updated 2026-10-28; published 2026-07-02; advisory modified 2026-09-10.

SimpleSAMLphp SP accepts a response from an unexpected IdP when unsigned `Response/InResponseTo` is combined with a signed assertion lacking `SubjectConfirmationData/InResponseTo`

Package: simplesamlphp/simplesamlphp Composer
Affected versions: >=2.5.0 and <2.5.2 or <2.4.7
Fixed in: 2.5.2, 2.4.7
Severity: high CVSS 7.1
Exploitation: not on CISA KEV · EPSS 0% (12.8th percentile)
Published: 2026-07-02
Source: osv.dev

References

CWE-345

NVD record simplesamlphp/simplesamlphp advisories

Am I affected?

Find out in one command. phpwarden checks your composer.lock against this advisory and 20,000+ others, ranked by real-world exploitation (CISA KEV + EPSS). Free, offline, open data.

# PHP projects (recommended)
composer require --dev phpwarden/phpwarden
# then
vendor/bin/phpwarden deps composer.lock

# or, without Composer
pipx install phpwarden   &&   phpwarden deps composer.lock

Or keep it checked automatically: GitHub Action · pre-commit hook · GitLab CI · Laravel artisan command

Install docs How findings are ranked

Related advisories

CVE-2018-6521 critical SimpleSAMLphp Use of insecure connection charset (sqlauth module) same package: simplesamlphp/simplesamlphp
CVE-2017-12869 high SimpleSAMLphp Authentication context bypass in the multiauth module same package: simplesamlphp/simplesamlphp
CVE-2017-12868 critical SimpleSAMLphp Session fixation issue and authentication bypass in the authcrypt module same package: simplesamlphp/simplesamlphp
CVE-2017-12873 critical Incorrect persistent NameID generation in SimpleSAMLphp same package: simplesamlphp/simplesamlphp
CVE-2017-12872 medium SimpleSAMLphp allows timing side-channel attacks same package: simplesamlphp/simplesamlphp
CVE-2016-3124 medium SimpleSAMLphp Information leakage issue in the sanitycheck module same package: simplesamlphp/simplesamlphp