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CVE-2026-77421— JLine: ReDoS in Nano Editor Regex Search Mode

Quick assessment

Affected
jline jline3
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

JLine is a Java library for handling console input. From 3.0.0 until 3.30.15 and 4.3.1, the JLine built-in nano editor's regex search mode passes a user-controlled search term from doSearch(String text) in builtins/src/main/java/org/jline/builtins/Nano.java to

CVSS 6.5 · Medium EPSS 0.43% · P35

Affected Version Matrix 2

VendorProduct Version RangeStatus
jline jline3 >= 3.0.0, < 3.30.15 affected
>= 4.0.0, < 4.3.1 affected
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I. Basic Information for CVE-2026-77421

Vulnerability Information

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Vulnerability Title
JLine: ReDoS in Nano Editor Regex Search Mode
Source: CVE Program / CVE List V5
Vulnerability Description
JLine is a Java library for handling console input. From 3.0.0 until 3.30.15 and 4.3.1, the JLine built-in nano editor's regex search mode passes a user-controlled search term from doSearch(String text) in builtins/src/main/java/org/jline/builtins/Nano.java to Java's backtracking regular expression engine without a timeout or backtracking bound. A nested-quantifier expression evaluated against non-matching buffer content can consume excessive CPU and indefinitely block the editor session thread, and remote multi-user deployments can lose a worker thread for each affected session. This issue is fixed in versions 3.30.15 and 4.3.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1333
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
jline jline3 >= 3.0.0, < 3.30.15 -

II. Public POCs for CVE-2026-77421

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III. Intelligence Information for CVE-2026-77421

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Patches & Fixes for CVE-2026-77421 (4)

Other References for CVE-2026-77421 (3)

Same Patch Batch · jline · 2026-09-23 · 4 CVEs total

CVE-2026-77422 7.5 HIGH JLine: ReDoS in Built-in grep Command Amplified by Automatic `.*` Wrapping
CVE-2026-77423 7.5 HIGH JLine: ReDoS in Built-in Less Viewer Search
CVE-2026-77420 5.5 MEDIUM JLine: ReDoS via `HISTORY_IGNORE` Configuration Variable

IV. Related Vulnerabilities

Same product: jline3
Same vendor: jline
Same weakness: CWE-1333

V. Comments for CVE-2026-77421

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