CVE-2026-56741
Prior to 3.30.14, 4.0.16, and 4.2.1, the JLine3 Telnet server remote-telnet module does not apply an upper bound to terminal dimensions received via the Telnet NAWS option, and TelnetIO.handleNAWS() in TelnetIO.java:856-879 reads client-supplied width…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.60%). 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 apply an upper bound to terminal dimensions received via the Telnet NAWS option, and TelnetIO.handleNAWS() in TelnetIO.java:856-879 reads client-supplied width and height as 16-bit unsigned integers and passes values such as 65535x65535 to setTerminalGeometry(), allowing an unauthenticated remote attacker to repeatedly alternate values and trigger continuous expensive rendering work that causes CPU exhaustion and denial of service. 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
- 0.60% probability · 48th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-400
- Affected
- jline/jline
- Source
- security-advisories@github.com
EPSS 0.6% 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/3ea9cad8699714dc072fade29d36be0d1e23d708Patch
- https://github.com/jline/jline3/commit/733eb353dca7b0ea0252e724445b6defa29c393ePatch
- https://github.com/jline/jline3/commit/86b7ba7801988aadb1a67555629522a71d603bd3Patch
- https://github.com/jline/jline3/pull/2000Issue 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/security/advisories/GHSA-2r2c-cx56-8933Vendor Advisory, Exploit
- https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933Vendor Advisory, Exploit
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.