{"id":"CVE-2021-43843","aliases":["GHSA-hp68-xhvj-x6j6"],"url":"https://o3.security/vulnerability/CVE-2021-43843","summary":"jsx-slack insufficient patch for CVE-2021-43838 ReDoS","details":"We found the patch for CVE-2021-43838 in jsx-slack v4.5.1 is insufficient to save from Regular Expression Denial of Service (ReDoS) attack.\n\nThis vulnerability affects to jsx-slack v4.5.1 and earlier versions.\n\n### Impact\n\nIf attacker can put a lot of JSX elements into `<blockquote>` tag _with including multibyte characters_, an internal regular expression for escaping characters may consume an excessive amount of computing resources.\n\n```javascript\n/** @jsxImportSource jsx-slack */\nimport { Section } from 'jsx-slack'\n\nconsole.log(\n  <Section>\n    <blockquote>\n      {[...Array(40)].map(() => (\n        <p>亜</p>\n      ))}\n    </blockquote>\n  </Section>\n)\n```\n\nv4.5.1 has released by passing the test against ASCII characters but missed the case of multibyte characters.\nhttps://github.com/yhatt/jsx-slack/security/advisories/GHSA-55xv-f85c-248q\n\n### Patches\n\njsx-slack v4.5.2 has updated regular expressions for escaping blockquote characters to prevent catastrophic backtracking. It is also including an updated test case to confirm rendering multiple tags in `<blockquote>` with multibyte characters.\n\n### References\n\n- https://github.com/yhatt/jsx-slack/commit/46bc88391d89d5fda4ce689e18ca080bcdd29ecc\n\n### Credits\n\nThanks to @hieki for finding out this vulnerability.","published":"2021-12-20T22:15:07.817Z","modified":"2026-07-09T01:06:16.472046Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.01916,"percentile":0.78007,"asOf":"2026-08-23"},"cisaKev":null,"exploitsKnown":2,"affectedPackages":[{"ecosystem":"npm","name":"jsx-slack","fixedVersion":"4.5.2"}],"fix":{"url":"https://github.com/yhatt/jsx-slack/commit/46bc88391d89d5fda4ce689e18ca080bcdd29ecc","label":"yhatt/jsx-slack@46bc883"},"references":[{"type":"ADVISORY","url":"https://github.com/yhatt/jsx-slack/releases/tag/v4.5.2"},{"type":"FIX","url":"https://github.com/yhatt/jsx-slack/commit/46bc88391d89d5fda4ce689e18ca080bcdd29ecc"},{"type":"FIX","url":"https://github.com/yhatt/jsx-slack/security/advisories/GHSA-55xv-f85c-248q"},{"type":"FIX","url":"https://github.com/yhatt/jsx-slack/security/advisories/GHSA-hp68-xhvj-x6j6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-43843"},{"type":"WEB","url":"https://github.com/yhatt/jsx-slack/security"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T01:06:16.472046Z"}}