CVE-2026-123802: Auth Bypass (CVSS 8.1)

Description

SuperTokens Core is an open source authentication server. From 11.3.0 until 11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1, and 12.3.1, a licensed deployment with a configured SAML client can authenticate an identity from an assertion that did not satisfy the audience check. When the identity provider uses assertion-level signing, an attacker who has a still-valid IdP-signed assertion naming the victim for any audience and the attacker's own valid assertion for the target audience can combine them because validateSamlResponseAudience accepts an audience from one assertion while extractAllClaims takes the final NameID and attributes from another; response-level signing does not expose this multi-assertion variant. Independently, an assertion from an identity provider configured for the target deployment but issued to another SuperTokens deployment using the shared default saml_sp_entity_id can satisfy the target's audience check. Successful exploitation authenticates the attacker as the victim IdP user. This issue is fixed in versions 11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1, and 12.3.1.

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CVSS v3.1 Score

8.1

HIGH

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

EPSS — Exploit Prediction

0.0030

Probability of exploitation

0.23%

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-287 Improper Authentication

CWE-345 CWE-345

CWE-1220 CWE-1220

References

Other References

Frequently Asked Questions

What is CVE-2026-123802? +

SuperTokens Core is an open source authentication server. From 11.3.0 until 11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1, and 12.3.1, a licensed deployment with a configured SAML client can authenticate an identity from an assertion that did not satisfy the audience check. When the identity provider uses assertion-level signing, an attacker who has a still-valid IdP-signed assertion naming the victim for any audience and the attacker's own valid assertion for the target audience can combine them because validateSamlResponseAudience accepts an audience from one assertion while extractAllClaims takes the final NameID and attributes from another; response-level signing does not expose this multi-assertion variant. Independently, an assertion from an identity provider configured for the target deployment but issued to another SuperTokens deployment using the shared default saml_sp_entity_id can satisfy the target's audience check. Successful exploitation authenticates the attacker as the victim IdP user. This issue is fixed in versions 11.3.8, 11.4.8, 12.0.11, 12.1.2, 12.2.1, and 12.3.1. It has a CVSS v3.1 base score of 8.1 (HIGH).

How severe is CVE-2026-123802? +

CVE-2026-123802 has a CVSS v3.1 score of 8.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0030, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-123802? +

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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