CVE-2026-56741

HIGH 7.5

JLine: Unauthenticated Remote DoS via Unbounded Telnet NAWS Terminal Geometry

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

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 65535x65535 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.

CWE	CWE-400
Vendor	jline
Product	jline3
Published	Jul 17, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Affected Versions

jline / jline3

< 3.30.14 >= 4.0.0, < 4.0.16 >= 4.1.0, < 4.2.1

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933 github.com: https://github.com/jline/jline3/pull/2000 github.com: https://github.com/jline/jline3/commit/3ea9cad8699714dc072fade29d36be0d1e23d708 github.com: https://github.com/jline/jline3/commit/733eb353dca7b0ea0252e724445b6defa29c393e github.com: https://github.com/jline/jline3/commit/86b7ba7801988aadb1a67555629522a71d603bd3 github.com: https://github.com/jline/jline3/releases/tag/4.0.16 github.com: https://github.com/jline/jline3/releases/tag/4.2.1