CVE-2026-77420Public exploitHinoki check available

Reader-thread hang via partially escaped history pattern

Published Sep 23, 2026 · Updated Sep 23, 2026

Inefficient regex processing in JLine 3.0.0 through 3.30.14 and 4.0.0 through 4.3.0 allows local users to hang a reader thread. DefaultHistory.matchPatterns translates HISTORY_IGNORE into a Java regex but leaves metacharacters such as parentheses and plus signs unescaped, enabling catastrophic backtracking. Exploitation requires control of application or user configuration; the pattern is reevaluated whenever a command enters history, consuming CPU and indefinitely blocking that reader session.

CVSS severity5.5
Medium
EPSS probability0.12%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Inefficient regex processing in JLine 3.0.0 through 3.30.14 and 4.0.0 through 4.3.0 allows local users to hang a reader thread. DefaultHistory.matchPatterns translates HISTORY_IGNORE into a Java regex but leaves metacharacters such as parentheses and plus signs unescaped, enabling catastrophic backtracking. Exploitation requires control of application or user configuration; the pattern is reevaluated whenever a command enters history, consuming CPU and indefinitely blocking that reader session.

The record

CVE
CVE-2026-77420
Published
Sep 23, 2026
Updated
Sep 23, 2026
Vendor
JLine
Product
JLine
Classifications
CWE-1333, T1499
Attack vector
local
Privileges
authenticated

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

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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 vectorlocal
Required privilegesauthenticated

What is affected?

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

Published CVSS scores

5.5GitHub Security AdvisoryCVSS:3.1/AV:L/AC:L/PR:L/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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499Endpoint Denial of Service

Public exploit references

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Technologies

Your stack

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