High [CVE-2026-73208] Authentication bypass via incorrect OAuth2 token validation
This high-severity Red Hat Linux advisory covers CVE-2026-73208 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9.
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Summary
An attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a scope claim, the audience claim is used in its place and checked against the configured required scopes.
A token that grants no relevant permissions can be accepted because its intended recipient value happens to match a configured scope name, granting access that should have been denied. It also hides an identity provider misconfiguration where scopes are not being issued at all.
Ensure the identity provider issues a scope claim for all tokens used with Dovecot, and that configured scope names do not match audience values. Update to non-vulnerable version.
No publicly available exploits are known. A flaw was found in Dovecot.
This vulnerability allows an attacker to bypass authentication by exploiting how OAuth2 tokens are validated. Red Hat severity: Important — CVSS 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N).
Weakness: CWE-303. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: dovecot.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- To mitigate this issue, ensure that the identity provider issues a scope claim for all tokens used with Dovecot. Additionally, verify that configured scope names in Dovecot do not match audience values from the identity provider. A restart of the Dovecot service may be required for configuration changes to take effect.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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