CVE-2026-56740
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…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.88%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.88% probability · 59th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-400
- Affected
- jline/jline
- Source
- security-advisories@github.com
EPSS 0.9% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/jline/jline3/commit/0389f0ee6d0375901b602671ad5dafd4d1d4ee09Patch
- https://github.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40Patch
- https://github.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194bPatch
- https://github.com/jline/jline3/pull/2000Issue Tracking
- https://github.com/jline/jline3/pull/2001Issue Tracking
- https://github.com/jline/jline3/releases/tag/4.0.16Release Notes
- https://github.com/jline/jline3/releases/tag/4.2.1Release Notes
- https://github.com/jline/jline3/releases/tag/jline-3.30.14Release Notes
- https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3fExploit, Vendor Advisory
- https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3fExploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.