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Vulnerability record · CVE-2026-56740 · published 17 July 2026

CVE-2026-56740: 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 limit the number of environment variables a client may inject via the Telnet NEW-ENVIRON option, and TelnetIO.readNEVariables() in TelnetIO.java:1127-1180 stores each variable pair in a HashMap held by ConnectionData, allowing an unauthenticated attacker to flood unique variable pairs before the terminating IAC SE byte and exhaust JVM heap memory with an OutOfMemoryError. This issue is fixed in versions 3.30.14, 4.0.16, and 4.2.1.

7.5 CVSS 3.1 High EPSS 0.88% · top 42.4% CWE-400 · Uncontrolled resource consumption
7.5CVSS 3.1 base score
0.88%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
10References, 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 limit the number of environment variables a client may inject via the Telnet NEW-ENVIRON option, and TelnetIO.readNEVariables() in TelnetIO.java:1127-1180 stores each variable pair in a HashMap held by ConnectionData, allowing an unauthenticated attacker to flood unique variable pairs before the terminating IAC SE byte and exhaust JVM heap memory with an OutOfMemoryError. 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/0389f0ee6d0375901b602671ad5dafd4d1d4ee09 Patch
https://github.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40 Patch
https://github.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194b Patch
https://github.com/jline/jline3/pull/2000 Issue Tracking
https://github.com/jline/jline3/pull/2001 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/releases/tag/jline-3.30.14 Release Notes
https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f ExploitVendor Advisory
https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f ExploitVendor Advisory

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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-2026-56740), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.