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

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-23 · updated 2026-09-30
• Weakness: CWE-1333

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.

Affected products

• jline3: from 3.0.0, < 3.30.15; from 4.0.0, < 4.3.1

References

• https://github.com/jline/jline3/commit/1d5fc3099e77938b971e197211cad2d4fbb17541
• https://github.com/jline/jline3/commit/341ee69ccc57b7733c1b40d6993219b64b3206ae
• https://github.com/jline/jline3/pull/2012
• https://github.com/jline/jline3/pull/2018
• https://github.com/jline/jline3/releases/tag/4.3.1
• https://github.com/jline/jline3/releases/tag/jline-3.30.15
• https://github.com/jline/jline3/security/advisories/GHSA-ph9c-7hw9-vhhw

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