CVE-2026-123538: Signature Bypass (CVSS 6.6)

Description

OpenAM before 16.1.4 does not verify that a signed SAML 1.x assertion or response was signed by the partner named as its issuer, accepting a signature from any certificate in OpenAM's keystore. An attacker holding such a private key, such as a trusted SAML 1.x partner, can forge assertions claiming another partner's issuer and sign in as that partner's users, including privileged ones.

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CVSS v3.1 Score

6.6

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0013

Probability of exploitation

0.03%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-347 CWE-347

References

Other References

https://github.com/OpenIdentityPlatform/OpenAM/security/advisories/GHSA-j56q-q3r3-hg7f https://www.vulncheck.com/advisories/openam-before-16.1.4-saml-1-x-signature-verification-issuer-impersonation

Frequently Asked Questions

What is CVE-2026-123538? +

OpenAM before 16.1.4 does not verify that a signed SAML 1.x assertion or response was signed by the partner named as its issuer, accepting a signature from any certificate in OpenAM's keystore. An attacker holding such a private key, such as a trusted SAML 1.x partner, can forge assertions claiming another partner's issuer and sign in as that partner's users, including privileged ones. It has a CVSS v3.1 base score of 6.6 (MEDIUM).

How severe is CVE-2026-123538? +

CVE-2026-123538 has a CVSS v3.1 score of 6.6 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0013, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-123538? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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