GHSA-2r2c-cx56-8933: JLine3 Telnet server: Unauthenticated Remote DoS via Unbounded Telnet NAWS Terminal Geometry

June 18, 2026

The JLine3 Telnet server (remote-telnet module) does not apply an upper bound to terminal dimensions received via the Telnet NAWS (Negotiate About Window Size) option. An unauthenticated remote attacker can send a NAWS subnegotiation advertising a 65535×65535 terminal and repeatedly alternate values to trigger continuous, expensive rendering work on the server, causing CPU exhaustion and denial of service.

References

github.com/advisories/GHSA-2r2c-cx56-8933
github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933

Code Behaviors & Features

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