CVE-2026-56741 – JLine: Unauthenticated Remote DoS via Unbounded Telnet NAWS Terminal Geometry

CVE ID :CVE-2026-56741

Published : July 17, 2026, 10:17 p.m. | 1 hour, 20 minutes ago

Description :JLine is a Java library for handling console input. Prior to 3.30.14, 4.0.16, and 4.2.1, the JLine3 Telnet server remote-telnet module does not apply an upper bound to terminal dimensions received via the Telnet NAWS option, and TelnetIO.handleNAWS() in TelnetIO.java:856-879 reads client-supplied width and height as 16-bit unsigned integers and passes values such as 65535×65535 to setTerminalGeometry(), allowing an unauthenticated remote attacker to repeatedly alternate values and trigger continuous expensive rendering work that causes CPU exhaustion and denial of service. This issue is fixed in versions 3.30.14, 4.0.16, and 4.2.1.

Severity: 7.5 | HIGH

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