CVE-2026-56740
Medium
Elevated severity or exploit probability.
CVSS base
7.5
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS — probability of exploitation (30 days)
0.9%
57.4th percentile
CISA KEV
Not listed
Weakness / dates
CWE-400
Published 2026-07-17 · modified 2026-08-18
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.
Affected
References
- https://github.com/jline/jline3/commit/0389f0ee6d0375901b602671ad5dafd4d1d4ee09
- https://github.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40
- https://github.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194b
- https://github.com/jline/jline3/pull/2000
- https://github.com/jline/jline3/pull/2001
- https://github.com/jline/jline3/releases/tag/4.0.16
- https://github.com/jline/jline3/releases/tag/4.2.1
- https://github.com/jline/jline3/releases/tag/jline-3.30.14
- exploit https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f
- exploit https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f