What is CVE-2026-56741?

CVE-2026-56741 is a high-severity vulnerability in Jline, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-07-17.

How severe is CVE-2026-56741?

High severity. CVSS v3 base score is 7.5 out of 10.

Resource exhaustion in Jline

CVE-2026-56741

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.

Vulnerability class: DoS (Denial of Service)

Published 2026-07-17 · last modified 2026-08-18.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.006 (47.8th percentile), scored 2026-10-24.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 48th percentile — 47.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.006 · change: -0.003

Affected products

Jline
Jline Jline3 — versions < 3.30.14, >= 4.0.0, < 4.0.16, >= 4.1.0, < 4.2.1

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933 (Exploit, Vendor Advisory)
github.com/jline/jline3/pull/2000 (Issue Tracking)
github.com/jline/jline3/commit/3ea9cad8699714dc072fade29d36be0d1e23d708 (Patch)
github.com/jline/jline3/commit/733eb353dca7b0ea0252e724445b6defa29c393e (Patch)
github.com/jline/jline3/commit/86b7ba7801988aadb1a67555629522a71d603bd3 (Patch)
github.com/jline/jline3/releases/tag/4.0.16 (Release Notes)
github.com/jline/jline3/releases/tag/4.2.1 (Release Notes)

Frequently asked questions

What is CVE-2026-56741?: CVE-2026-56741 is a high-severity vulnerability in Jline, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-07-17.
How severe is CVE-2026-56741?: High severity. CVSS v3 base score is 7.5 out of 10.