Service interruption via backtracking-amplified grep regex
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 remote attackers to hang shell workers. PosixCommands.grep wraps each user-supplied expression with dot-star before Java's backtracking engine compiles it, expanding catastrophic backtracking on nonmatching input. Exposure requires an application to provide the built-in grep command; remotely exposed shells let repeated requests occupy worker threads indefinitely.
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 remote attackers to hang shell workers. PosixCommands.grep wraps each user-supplied expression with dot-star before Java's backtracking engine compiles it, expanding catastrophic backtracking on nonmatching input. Exposure requires an application to provide the built-in grep command; remotely exposed shells let repeated requests occupy worker threads indefinitely.
The record
- CVE
- CVE-2026-77422
- Published
- Sep 23, 2026
- Updated
- Sep 23, 2026
- Vendor
- JLine
- Product
- JLine
- Classifications
- CWE-1333, T1499.003
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 23, 2026CVE publishedPublication date reported by the CVE source.
- 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.
- Affected versionversion=>= 3.0.0, < 3.30.15
- Affected versionversion=>= 4.0.0, < 4.3.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- Upstream built-in grep ReDoS proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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