Medium [CVE-2026-42008] Authentication bypass via trusted proxy forwarding
This medium-severity Red Hat Linux advisory covers CVE-2026-42008 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
Forwarding information received from a host listed as a trusted proxy is not kept separate from Dovecot's own authentication fields, so a value sent by that host can be injected as an internal authentication field. Any host permitted to act as a trusted proxy can authenticate as any user without knowing that user's password.
This affects deployments whose password database honours a field that permits authentication without a password. Deployments that do not configure trusted proxies are not affected.
Restrict the list of trusted proxy networks to hosts that are fully under your control. Update to non-vulnerable version.
No publicly available exploits are known. A flaw was found in Dovecot.
Red Hat severity: Moderate — CVSS 4.3 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N). Weakness: CWE-349.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9. Will not fix / out of support: Red Hat Enterprise Linux 6.
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 1 hour 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 1 hour ago·verify at source
Mitigation checklist
- To mitigate this issue, ensure that the `auth_proxy_trusted_networks` configuration in Dovecot is strictly limited to only trusted hosts that are fully under administrative control. Review and restrict the `auth_proxy_trusted_networks` setting in your Dovecot configuration (e.g., `/etc/dovecot/conf.d/10-auth.conf` or similar) to prevent unauthorized hosts from acting as trusted proxies. If trusted proxies are not required, remove this configuration entirely. A restart of the Dovecot service may be required for changes to take effect.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
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