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Vulnerability record · CVE-2026-56741 · published 17 July 2026

CVE-2026-56741: Jline uncontrolled resource consumption vulnerability

Jline · Jline

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.

7.5 CVSS 3.1 High EPSS 0.89% · top 42.3% CWE-400 · Uncontrolled resource consumption
7.5CVSS 3.1 base score
0.89%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References, 2 tagged exploit
18 Aug 2026Last modified by NVD

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 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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/jline/jline3/commit/3ea9cad8699714dc072fade29d36be0d1e23d708 Patch
https://github.com/jline/jline3/commit/733eb353dca7b0ea0252e724445b6defa29c393e Patch
https://github.com/jline/jline3/commit/86b7ba7801988aadb1a67555629522a71d603bd3 Patch
https://github.com/jline/jline3/pull/2000 Issue Tracking
https://github.com/jline/jline3/releases/tag/4.0.16 Release Notes
https://github.com/jline/jline3/releases/tag/4.2.1 Release Notes
https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933 Vendor AdvisoryExploit
https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933 Vendor AdvisoryExploit

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-56741), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.