Vulnerability · Published Oct 7, 2026 · Assigned by redhat

CVE-2026-107121Keycloak-services: keycloak-services: smtp starttls plaintext credential and message downgrade

Medium 6.5

In plain English

A medium-severity security flaw in Red Hat Build of Keycloak from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 0% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)<0.1%top 99.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

A flaw was found in the SMTP email configuration handling of the keycloak-services component. When the STARTTLS option is enabled, Keycloak fails to strictly enforce an encrypted connection, allowing it to fall back to unencrypted communication if the encryption request is tampered with. An attacker who can intercept network traffic can exploit this to capture sensitive email credentials and message content in plain text.

Affected products (as reported)

Vendor	Product	Versions
Red Hat	Red Hat Build of Keycloak	see references
Red Hat	Red Hat Build of Keycloak	see references
Red Hat	Red Hat Single Sign-On 7	see references

Weakness: CWE-319 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

References

https://access.redhat.com/security/cve/CVE-2026-107121 vdb-entry, x_refsource_REDHAT
RHBZ#2547296 issue-tracking, x_refsource_REDHAT