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Fencer Vulns
high 7.5

CVE-2026-56741 json

JLine: Unauthenticated Remote DoS via Unbounded Telnet NAWS Terminal Geometry

published 2026-06-18 4 mo ago modified 2026-10-24 15 d ago also EUVD-2026-45342 , GHSA-2r2c-cx56-8933

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits
0
none known

Summary

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.

Patch / fix

  • maven org.jline:jline-remote-telnet 3.30.14, 4.0.16, 4.2.1
  • jline jline 3.30.14, 4.0.16, 4.2.1
  • org.jline jline-remote-telnet 3.30.14, 4.0.16, 4.2.1
  • jline3 SLES for SAP applications 16.0, SLES 16.0 3.30.15-160000.1.1

suse advisories SUSE-SU-2026:22856-1

  • jline3 openSUSE Leap 16.0 3.30.15-160000.1.1
  • jline3 openSUSE Tumbleweed 3.30.15-3.1

opensuse advisories openSUSE-SU-2026:21423-1openSUSE-SU-2026:11338-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-56741 updated cvss 7.5

org.jline/jline-remote-telnet: JLine3 Telnet server: Denial of Service via uncontrolled terminal dimensions

  • Red Hat Fuse 7 jline-remote-telnet
    not affected: vulnerable code not present
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-spark-operator-rhel9, rhoai/odh-th-torch-cpu-py312-rhel9, rhoai/odh-th-torch-cuda-py312-rhel9, rhoai/odh-th06-cpu-torch210-py312-rhel9, rhoai/odh-th06-cpu-torch291-py312-rhel9, rhoai/odh-th06-rocm64-torch291-py312-rhel9, +2 more
    not affected: vulnerable code not in execute path

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.60% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
maven org.jline:jline-remote-telnet
>=4.1.0, <4.2.1
>=4.0.0, <4.0.16
<3.30.14
4.2.1
4.0.16
3.30.14

Affected products

  • jline jline3

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.