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Full vulnerability report · 2026
CVE-2026-56741High confidence

JLine: Unauthenticated Remote DoS via Unbounded Telnet NAWS Terminal Geometry

jline · jline3

Official source article: GitHub GHSA-2R2C-CX56-8933 ↗. Check the applicable product and release in the original source.

7.5HighCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 20 Jul 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.89% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs jline jline3 and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

15 package states
Package result overrides the generic status

BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 4 affected package states shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.

Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourcejlineUnder evaluationDebian has not confirmed a fixed package state for this release.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian trixietrixie · sourcejline2Under evaluationDebian has not confirmed a fixed package state for this release.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian trixietrixie · sourcejline3Affected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcejlineUnder evaluationDebian has not confirmed a fixed package state for this release.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcejline2Under evaluationDebian has not confirmed a fixed package state for this release.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcejline3Affected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcejlineUnder evaluationDebian has not confirmed a fixed package state for this release.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcejline2Under evaluationDebian has not confirmed a fixed package state for this release.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcejline3Affected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcejlineUnder evaluationDebian has not confirmed a fixed package state for this release.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcejline2Under evaluationDebian has not confirmed a fixed package state for this release.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcejline3Affected, no fix publishedDebian currently tracks this release as open.Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivejlineUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivejline2Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivejline3Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Open-source package ranges6 source-attributed ranges

These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.

Ecosystem and packageAffected rangeFirst fixed versionEvidence
Mavenorg.jline:jline-remote-telnetECOSYSTEM: introduced 4.1.0; fixed 4.2.14.2.1OSV record ↗aggregator derived · 10 Sep 2026
Mavenorg.jline:jline-remote-telnetECOSYSTEM: introduced 4.0.0; fixed 4.0.164.0.16OSV record ↗aggregator derived · 10 Sep 2026
Mavenorg.jline:jline-remote-telnetECOSYSTEM: introduced 0; fixed 3.30.143.30.14OSV record ↗aggregator derived · 10 Sep 2026
mavenorg.jline:jline-remote-telnet>= 4.1.0, < 4.2.14.2.1GitHub advisory ↗upstream repository advisory · 1 Sep 2026
mavenorg.jline:jline-remote-telnet>= 4.0.0, < 4.0.164.0.16GitHub advisory ↗upstream repository advisory · 1 Sep 2026
mavenorg.jline:jline-remote-telnet< 3.30.143.30.14GitHub advisory ↗upstream repository advisory · 1 Sep 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-56741 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityorg.jline/jline-remote-telnet: JLine3 Telnet server: Denial of Service via uncontrolled terminal dimensions
1 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • rhoai/odh-spark-operator-rhel9 as a component of Red Hat OpenShift AI (RHOAI)
Summary
A flaw was found in the JLine3 Telnet server's remote-telnet module. An unauthenticated remote attacker can exploit this vulnerability by repeatedly sending large terminal dimension values through the Telnet Negotiate About Window Size (NAWS) option. This action triggers continuous, resource-intensive rendering processes, leading to CPU exhaustion and a denial of service (DoS) for the server.
Remediation
Affected
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-45342

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

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.

What

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.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

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.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
a network path → Uncontrolled Resource Consumption → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-400 ↗

CWE-400: Uncontrolled Resource Consumption. The product does not properly control the allocation and maintenance of a limited resource.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-400Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

Cyber Security Agency of Singapore · English · CSA-SB-20260722Security Bulletin 22 Jul 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 22 Jul 2026, published on 22 July 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-028978jlineにおけるリソースの枯渇に関する脆弱性

JLineはコンソール入力を処理するためのJavaライブラリです。バージョン3.30.14、4.0.16、および4.2.1より前のJLine3 Telnetサーバのremote-telnetモジュールは、Telnet NAWSオプション経由で受け取った端末のサイズに上限を適用しておらず、TelnetIO.javaのTelnetIO.handleNAWS()メソッド（856〜879行目）ではクライアントから提供された幅と高さを16ビット符号なし整数として読み取り、65535×65535などの値をsetTerminalGeometry()に渡します。これにより、認証されていないリモート攻撃者が値を繰り返し切り替えて連続的に高負荷なレンダリング処理を誘発し、CPU枯渇とサービス拒否（DoS）を引き起こす可能性があります。この問題はバージョン3.30.14、4.0.16、および4.2.1で修正されています。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
rhoai/odh-spark-operator-rhel9 as a component of Red Hat OpenShift AI (RHOAI)
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 17 Jul 2026 · Last source change 20 Jul 2026, 15:21 UTC · CWE-400 · Uncontrolled Resource Consumption

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-45342
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    rhoai/odh-spark-operator-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cpu-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cuda-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI)
    After
    rhoai/odh-spark-operator-rhel9 as a component of Red Hat OpenShift AI (RHOAI)
    Red Hat Product Security ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    jline-remote-telnet as a component of Red Hat Fuse 7; rhoai/odh-spark-operator-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cpu-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cuda-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI)
    After
    rhoai/odh-spark-operator-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cpu-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cuda-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI)
    Red Hat Product Security ↗
  3. Affected versionsThe structured affected or fixed version information changed.
    Before
    jline-remote-telnet as a component of Red Hat Fuse 7; rhoai/odh-spark-operator-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cpu-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cuda-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th06-cpu-torch210-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th06-cpu-torch291-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th06-cuda130-torch210-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th06-cuda130-torch291-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th06-rocm64-torch291-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI)
    After
    jline-remote-telnet as a component of Red Hat Fuse 7; rhoai/odh-spark-operator-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cpu-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI); rhoai/odh-th-torch-cuda-py312-rhel9 as a component of Red Hat OpenShift AI (RHOAI)
    Red Hat Product Security ↗
  4. Vendor guidanceAuthoritative vendor guidance changed: added patch: github.com/3ea9cad8699714dc072fade29d36be0d1e23d708; added patch: github.com/733eb353dca7b0ea0252e724445b6defa29c393e; 3 further additions.
    Before
    no authoritative guidance recorded
    After
    patch: github.com/3ea9cad8699714dc072fade29d36be0d1e23d708 · patch: github.com/733eb353dca7b0ea0252e724445b6defa29c393e · patch: github.com/86b7ba7801988aadb1a67555629522a71d603bd3 · 2 more references
    github.com ↗
  5. Affected versionsThe structured affected or fixed version information changed.
    Before
    < 3.30.14; >= 4.0.0, < 4.0.16; >= 4.1.0, < 4.2.1 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    < 3.30.14; >= 4.0.0, < 4.0.16; >= 4.1.0, < 4.2.1 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  6. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    github.com ↗
  7. Public exploit evidencePublic exploit evidence changed from Public exploit reference to Public exploit reference.
    Before
    Public exploit reference
    After
    Public exploit reference
    github.com ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-45342↗Vendor CSAF · Red Hat Product Security↗CISA Vulnrichment SSVC evidence↗Public exploit reference · GitHub GHSA-2R2C-CX56-8933↗Patch or update reference↗Patch or update reference↗Patch or update reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-56741 · cve.blacktree.nl