CVE-2026-56740 — Security Box Score

CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-56740HIGH

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

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  N  N  H    7.5   .0053   42.3     —

AFFECTED
  Product  Versions     Fixed
  jline3   < 3.30.14 –  —

TIMELINE
  Jun 22  Reserved by GitHub_M
  Jul 17  EXPLOIT PUBLISHED — CVE-2026-56740 (jline3). Public exploit reference added.
  Jul 17  Published (CNA: GitHub_M)

CWE-400 · CNA: GitHub_M · CVSS v3.1 · 9 references · NVD status: Analyzed

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
June 22, 2026	Reserved	Reserved by GitHub_M
July 17, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-56740 (jline3). Public exploit reference added.
July 17, 2026	Published	Published (CNA: GitHub_M)

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
jline	jline3	—	< 3.30.14	—

Weaknesses

CWE-400

References (9)

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 [Exploit, Vendor Advisory]

Authoritative record: CVE-2026-56740 at cve.org

Vendors: jline

Weaknesses: CWE-400

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-56740 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.