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`
Attackers can bypass IdP selection controls in SimpleSAMLphp by exploiting SAML response validation flaws, potentially accessing unauthorized data.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-49284?
CVE-2026-49284 is a high-severity authentication bypass vulnerability in simplesamlphp, published on 17 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
SimpleSAMLphp versions before 1.18.6 contain an information disclosure vulnerability. Prior to 2.4.7 and 2.5.2, SimpleSAMLphp's SAML SP ACS path does not enforce the IdP selected for an SP-initiated login when unsigned Response/InResponseTo is combined with a signed assertion lacking SubjectConfirmationData/InResponseTo, allowing a response issued by one trusted IdP to be bound to SP state created for another IdP and bypass flows that route users to a specific IdP, including deployments that set enable_unsolicited to false. This issue is fixed in versions 2.4.7 and 2.5.2.
Weakness: CWE-345
Which versions are affected by CVE-2026-49284?
4 open source packages ship an affected version, including simplesamlphp/simplesamlphp. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
simplesamlphp/simplesamlphp Packagist | All versions | 2.4.7 |
simplesamlphp/simplesamlphp Packagist | All versions | 2.4.7 |
simplesamlphp/simplesamlphp Packagist | From 2.5.0 | 2.5.2 |
simplesamlphp/simplesamlphp Packagist | From 2.5.0 | 2.5.2 |
Products include Simplesamlphp Simplesamlphp.
How do I fix CVE-2026-49284?
Upgrade simplesamlphp/simplesamlphp to a fixed version for your release line: 2.4.7 or 2.5.2.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-49284 being exploited?
There is no known exploitation of CVE-2026-49284 in the wild and no public exploit code.
Other vulnerabilities in simplesamlphp
- CVE-2017-12868 SimpleSAMLphp Session fixation issue and authentication bypass in the authcrypt module
- CVE-2018-7644 SimpleSAMLphp Improper Verification of Cryptographic Signature
- CVE-2018-6520 SimpleSAMLphp Open redirection protection bypass
- CVE-2017-12870 SimpleSAMLphp Unauthenticated encryption in CBC mode
- CVE-2017-12871 SimpleSAMLphp Incorrect IV generation for encryption
Sources
Also known as DEBIAN-CVE-2026-49284, GHSA-q8r6-xj3f-wrrm, UBUNTU-CVE-2026-49284.