High 7.5Published Jul 17, 2026

CVE-2026-56740JLine: Unauthenticated Remote Memory Exhaustion via Unbounded Telnet NEW-ENVIRON Variables

Updated under an hour ago (Oct 27, 2026, 5:50 PM ET)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-400
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Jul 20, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

jline jline3 jline:jline3 (from the name)	before 3.30.14; from 4.0.0, < 4.0.16; from 4.1.0, < 4.2.1	CNA record
jline jline jline:jline	before 3.30.14; from 4.0.0 before 4.0.16; from 4.1.0 before 4.2.1	NVD

References

References

https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f	x-refsource-confirm, exploit, vendor-advisory
https://github.com/jline/jline3/pull/2000	x-refsource-misc, issue-tracking
https://github.com/jline/jline3/pull/2001	x-refsource-misc, issue-tracking
https://github.com/jline/jline3/commit/0389f0ee6d0375901b602671ad5dafd4d1d4ee09	x-refsource-misc, patch
https://github.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40	x-refsource-misc, patch
https://github.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194b	x-refsource-misc, patch
https://github.com/jline/jline3/releases/tag/4.0.16	x-refsource-misc, release-notes
https://github.com/jline/jline3/releases/tag/4.2.1	x-refsource-misc, release-notes
https://github.com/jline/jline3/releases/tag/jline-3.30.14	x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.