# CVE-2026-77420: JLine: ReDoS via `HISTORY_IGNORE` Configuration Variable > An attacker controlling configuration can trigger a ReDoS attack in JLine, causing excessive CPU usage and blocking the reader thread. - **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 23 Sep 2026 - **Updated:** 29 Sep 2026 - **Also known as:** CLEANSTART-2026-AA89451, CLEANSTART-2026-AQ28324, CLEANSTART-2026-HM88327, CLEANSTART-2026-IR34711, CLEANSTART-2026-KE95640, CLEANSTART-2026-MF43595, CLEANSTART-2026-SQ10175, CLEANSTART-2026-ZH81930, DEBIAN-CVE-2026-77420, ECHO-cfa0-39d5-b1d1, GHSA-5q95-hrpc-m3w3, MINI-2mjq-5fh8-rm6p, MINI-3ggc-f4j6-g56j, MINI-3h63-6vmx-x4m4, MINI-3xrp-72jv-94f9, MINI-4337-p896-jqgh, MINI-44v4-v8wc-584r, MINI-458m-2p3r-c77p, MINI-4fcp-hv9h-mhhr, MINI-4h7v-v4vq-c79w, MINI-4jc9-f7m2-fjp9, MINI-4x72-f42p-743m, MINI-55c8-86j5-32q9, MINI-5726-9c87-vmrh, MINI-58vx-vg5x-phv7, MINI-5ghg-g585-hjv6, MINI-5jh9-3cg8-x4mp, MINI-66gx-6phf-c2c5, MINI-6c6m-wxpf-xcc6, MINI-6m52-rppf-4x5x, MINI-6mp6-fv45-v6x6, MINI-6vgc-vxrp-vqww, MINI-7629-6vjf-xprf, MINI-843j-2gh6-j2fj, MINI-87mv-qc28-6x69, MINI-8cwj-pmp6-563v, MINI-9ff9-5c5w-3964, MINI-fjvx-3f66-xxjw, MINI-fpr2-g6hf-8fvc, MINI-g66j-254p-7c79, MINI-h5v3-fjr8-cjhh, MINI-jvxm-qjw6-78fp, MINI-mjxx-5fgq-c7fq, MINI-mr45-q8gv-cw7f, MINI-p466-pqrp-3g56, MINI-pm9j-m4w4-w675, MINI-q3jp-6w83-4j3q, MINI-r47r-4r74-jc55, MINI-r982-56wh-m96p, MINI-rffw-q8r8-gx45, MINI-rg49-qh84-j6vm, MINI-rw83-whw5-gf56, MINI-rx9x-q5mw-39x3, MINI-vgf2-rf3r-66g9, MINI-w9xg-m8xg-x9m8, MINI-wh6h-h3hr-qf48, MINI-wp5v-whx2-73w9, MINI-x64c-364g-phh6, MINI-x7cr-8mvq-hvrq, UBUNTU-CVE-2026-77420 ## What is CVE-2026-77420? CVE-2026-77420 is a medium-severity denial of service vulnerability in jline3, published on 23 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description JLine is a Java library for handling console input. From 3.0.0 until 3.30.15 and 4.3.1, DefaultHistory.matchPatterns(String patterns, String line) in reader/src/main/java/org/jline/reader/impl/history/DefaultHistory.java converts the HISTORY_IGNORE configuration value into a Java regular expression while escaping only part of its syntax, allowing other regex metacharacters to reach the backtracking engine. An attacker who can control application or user configuration can supply a nested-quantifier expression that is reevaluated whenever a command is added to history, consuming excessive CPU and indefinitely blocking the reader thread. This issue is fixed in versions 3.30.15 and 4.3.1. Weakness: CWE-1333 (Inefficient Regular Expression Complexity) ## Which versions are affected by CVE-2026-77420? 4 open source packages ship an affected version, including org.jline:jline-reader. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.jline:jline-reader` | Maven | From 3.0.0 | 3.30.15 | | `org.jline:jline-reader` | Maven | From 3.0.0 | 3.30.15 | | `org.jline:jline-reader` | Maven | From 4.0.0 | 4.3.1 | | `org.jline:jline-reader` | Maven | From 4.0.0 | 4.3.1 | ## How do I fix CVE-2026-77420? Upgrade org.jline:jline-reader to a fixed version for your release line: 3.30.15 or 4.3.1. ## Is CVE-2026-77420 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77420 exists. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-77420 and fix it if it is affected. What it is: CVE-2026-77420 is a medium-severity denial of service vulnerability in jline3, published on 23 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77420 exists. Affected packages and fixed versions: - org.jline:jline-reader (Maven): affected from 3.0.0; fixed in 3.30.15 - org.jline:jline-reader (Maven): affected from 3.0.0; fixed in 3.30.15 - org.jline:jline-reader (Maven): affected from 4.0.0; fixed in 4.3.1 - org.jline:jline-reader (Maven): affected from 4.0.0; fixed in 4.3.1 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-77420/ (Markdown: https://insights.sbomify.com/CVE-2026-77420/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77420 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77420 - OSV: https://osv.dev/vulnerability/CVE-2026-77420 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-77420/ Summaries are generated and may contain mistakes; the official description above is the record.