CVE-2026-34486

CVE-2026-34486 is a missing-encryption vulnerability in Apache Tomcat in which the EncryptInterceptor, the component that encrypts Tomcat cluster communication, can be bypassed in a fail-open manner; the flaw was introduced as a regression by the fix for CVE-2026-29146. It affects Tomcat 11.0.20, 10.1.53 and 9.0.116, and is triggered when cluster communication is expected to be encrypted: an attacker positioned on the network path between cluster nodes receives inter-node traffic in cleartext. By reading that unencrypted traffic, the attacker can obtain sensitive data such as session payloads, potentially enabling session theft and authentication bypass as indicated by related reporting. Only deployments running the affected point releases with the EncryptInterceptor in use are impacted, including Tomcat shipped in Red Hat JBoss Web Server and Red Hat Enterprise Linux channels. The flaw is being actively exploited: CISA added it to the Known Exploited Vulnerabilities catalog on 2026-08-04, EPSS places 30-day exploitation probability at 98.6%, though no public proof-of-concept is known and ransomware use is unconfirmed.

What to do: Upgrade Apache Tomcat to 11.0.21, 10.1.54 or 9.0.117, and apply the corresponding Red Hat JBoss Web Server / Enterprise Linux updates when published. Audit Tomcat cluster configurations for EncryptInterceptor usage, and until patched restrict or encrypt the network segment carrying inter-node cluster traffic. Because the flaw is in CISA's KEV catalog, federal agencies must patch per BOD 26-04 timelines and should review cluster nodes for signs of session data interception.