CVE-2026-77423Public exploitNetwork attack vectorHinoki check available

Service interruption via unbounded regex backtracking

Published Sep 23, 2026 · Updated Sep 23, 2026

Regular expression denial of service in JLine 3.0.0 through 3.30.14 and 4.0.0 through 4.3.0 allows attackers to hang less sessions. Less.getPattern() compiles user-controlled search and display-filter text as Java backtracking regular expressions, then repeatedly applies them to file lines without a timeout or backtracking bound. Reachability requires use of the built-in less viewer; one local session can hang, while exposed Telnet or SSH deployments can lose a bounded worker pool across repeated sessions.

CVSS severity7.5
High
EPSS probability0.39%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Get started

Summary

What happened

Regular expression denial of service in JLine 3.0.0 through 3.30.14 and 4.0.0 through 4.3.0 allows attackers to hang less sessions. Less.getPattern() compiles user-controlled search and display-filter text as Java backtracking regular expressions, then repeatedly applies them to file lines without a timeout or backtracking bound. Reachability requires use of the built-in less viewer; one local session can hang, while exposed Telnet or SSH deployments can lose a bounded worker pool across repeated sessions.

The record

CVE
CVE-2026-77423
Published
Sep 23, 2026
Updated
Sep 23, 2026
Vendor
JLine
Product
JLine
Classifications
CWE-1333, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 23, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.0.0, < 3.30.15
  2. Affected versionversion=>= 4.0.0, < 4.3.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

JLine · JLineversion=>= 3.0.0, < 3.30.15; version=>= 4.0.0, < 4.3.1

Published CVSS scores

7.5JLineCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Get started to see how Hinoki identifies affected software and validates exploitability in your environment.

Get started