How severe is GHSA-46r4-f8gj-xg56?

GHSA-46r4-f8gj-xg56 has a CVSS score of 8.6/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-46r4-f8gj-xg56?

GHSA-46r4-f8gj-xg56 affects the following packages: simplesamlphp/saml2 (Packagist), simplesamlphp/saml2 (Packagist), simplesamlphp/saml2-legacy (Packagist). Ecosystems affected: Packagist.

How do I fix GHSA-46r4-f8gj-xg56?

Update simplesamlphp/saml2 to 4.17.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-46r4-f8gj-xg56 is resolved across your whole dependency graph.

How do I detect GHSA-46r4-f8gj-xg56 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for simplesamlphp/saml2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-46r4-f8gj-xg56 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-46r4-f8gj-xg56?

O3 pinpoints whether GHSA-46r4-f8gj-xg56 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-46r4-f8gj-xg56 actively exploited in the wild?

No public exploit code has been indexed for GHSA-46r4-f8gj-xg56 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-46r4-f8gj-xg56?

GHSA-46r4-f8gj-xg56 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 21th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-46r4-f8gj-xg56?

GHSA-46r4-f8gj-xg56 is classified as CWE-347 (CWE-347). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-46r4-f8gj-xg56 published, and has it been updated?

GHSA-46r4-f8gj-xg56 was published on March 11, 2025 and was last updated on May 9, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

GHSA-46r4-f8gj-xg56

HIGH

The SimpleSAMLphp SAML2 library incorrectly verifies signatures for HTTP-Redirect binding

Also known asCVE-2025-27773

Published

Mar 11, 2025

Updated

May 9, 2025

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk21th percentile+0.14%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

3 pkgs affected

🐘simplesamlphp/saml2🐘simplesamlphp/saml2🐘simplesamlphp/saml2-legacy

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Summary

There's 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.

I believe that it exists for v4 only. I have not yet developed a PoC.

V5 is well designed and instead builds the signed query from the same message that will be consumed.

Details

What is verified

The data['SignedQuery'] is the string that will be verified by the public key.

It is defined here: https://github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php#L178-L217

THe code will iterate through each parameter name. Notably, sigQuery is overridden each time when processing, making the last of SAMLRequest/SAMLResponse used for sigQuery.

For example, given:

SAMLRequest=a&SAMLResponse=idpsigned

SAMLResponse=idpsigned will be set as sigQuery, then later verified

What is actually processed

Processing uses SAMLRequest parameter value first, (if it exists) then SAMLResponse:

https://github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/src/SAML2/HTTPRedirect.php#L104-L113

Given this, the contents that are processed might not be the same as the data that is actually verified.

Exploiting

Suppose an attacker has a signed HTTP Redirect binding from IdP, say a signed logout response. :

SAMLResponse=idpsigned&RelayState=...&SigAlg=...&Signature

Then an attacker can append SAMLRequest in front:

SAMLRequest=unverifieddata&SAMLResponse=idpsigned&RelayState=...&SigAlg=...&Signature=..

SimpleSAMLPhp will only verify the SAMLResponse, but will actually use the SAMLRequest contents. The impact here is increased because there's no checks that SAMLRequest actually contains a Request, it could instead contain an Response, which allows the attacker to effectively impersonate any user within the SP.

IdPs

Microsoft Azure AD/Entra (and likely ADFS) signs the LogoutResponse via this SimpleSign format in HTTP Redirect binding. If an attacker logs out of Entra, they will be able to extract a valid Signature.

Attached is an HTTP Request when an I initiated a SLO request from the service provider to the IdP (entra). Then IdP POSTed this SAMLResponse with HTTP Redirect binding signature, via the user browser to the SP. It should be possible to carry out the described attack with this.

https://webhook.site/c6038292-6ef5-46ac-973d-d7c25520ec48/logout?SAMLResponse=fVJNa%2bMwEP0rRndZtmw5tnAMy%2fYSaC9N6aGXIsmjVMTRGI9M%2bvObdeihsPQ4w7x5HzM9mcs060c84ZqegWaMBNnhYc%2fejS1UW1TAnVU7XldK8s7JkcvOd60Db3zTsewVFgoY90zmBcsORCscIiUT061VyJqXJS%2fbl7LRUmrZ5mXdvLHsASiFaNKG%2fEhpJi3EFewH4jmnkEC4pqha2UnegFe8bozj3a4a%2bbhzUilZgKtbMW2yb7TxW%2foL7lkM9hTC2XnEOPvZXjDECb2N1lh7mvBsp%2bnsErDs8zJF0lsEe7YuUaOhQDqaC5BOTh%2f%2fPD3qmzE9L5jQ4cSGfrO43KG%2fgwwRLP8ssuHbIiXKryGOeKU8QhLSVN7WteejV8Bru%2bt4WynFbwE3bdVV5ahG0Ys759Dfj3VMJq30s%2fqLI2SvZlrhd020Tevj6hwQMTH04udS8b%2bHGL4A&Signature=Z%2f7gIPv7Gkgvqtwo0bzgXyum9IjHMfP0zTYuNbl%2fBUGlQ%2fU%2bbOZGZJ6Rk9wLUyvNQ5XlZRxZrfESNA%2bn0CVyIedsg9GxQKTi7VqPTJFJqEIP1BZaEpYYP3%2f6sFfLxfTMKecJoQdxnDE5Malte1hMj2UujWnLXOnp0CgO%2f%2fU2K52SoGckIzNDRB%2fJ6%2fysTn%2bDjBrmgdro%2fgdTyby9%2f3vm8dzY8pUkRCgMjlimShrZxr5U33wQvwPLIXlDgActr91RUtWKE0k8sy%2brshrK9DKLPo8AdTLk7NYhjSWdF7OG7uqgEeEo470tacqQuA09E0qDh8CWS%2bycLJijiGYWVyQa4Q%3d%3d&SigAlg=http%3a%2f%2fwww.w3.org%2f2001%2f04%2fxmldsig-more%23rsa-sha256

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`simplesamlphp/saml2`	all versions	4.17.0
🐘Packagist	`simplesamlphp/saml2`	≥ 5.0.0-alpha.1&&< 5.0.0-alpha.20	5.0.0-alpha.20
🐘Packagist	`simplesamlphp/saml2-legacy`	all versions	4.17.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for simplesamlphp/saml2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update simplesamlphp/saml2 to 4.17.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-46r4-f8gj-xg56 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-46r4-f8gj-xg56 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-46r4-f8gj-xg56. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary There's 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. I believe that it exists for v4 only. I have not yet developed a PoC. V5 is well designed and instead builds the signed query from the same message that will be consumed. ### Details #### What is verified The data['SignedQuery'] is the string that will be verified by the public key. It is defined here: https://github.com/simplesamlphp/saml2/blob/9545abd0d9d48388f2fa00469c5c1e0294f0303e/

O3 Security · Impact-Aware SCA

Is GHSA-46r4-f8gj-xg56 in your dependencies?

O3 detects GHSA-46r4-f8gj-xg56 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works