{"id":"CVE-2024-28243","aliases":["GHSA-64fm-8hw2-v72w"],"url":"https://o3.security/vulnerability/CVE-2024-28243","summary":"KaTeX's maxExpand bypassed by \\edef","details":"### Impact\nKaTeX users who render untrusted mathematical expressions could encounter malicious input using `\\edef` that causes a near-infinite loop, despite setting `maxExpand` to avoid such loops. This can be used as an availability attack, where e.g. a client rendering another user's KaTeX input will be unable to use the site due to memory overflow, tying up the main thread, or stack overflow.\n\n### Patches\nUpgrade to KaTeX v0.16.10 to remove this vulnerability.\n\n### Workarounds\nForbid inputs containing the substring `\"\\\\edef\"` before passing them to KaTeX.\n(There is no easy workaround for the auto-render extension.)\n\n### Details\nKaTeX supports an option named `maxExpand` which prevents infinitely recursive macros from consuming all available memory and/or triggering a stack overflow error. However, what counted as an \"expansion\" is a single macro expanding to any number of tokens. The expand-and-define TeX command `\\edef` can be used to build up an exponential number of tokens using only a linear number of expansions according to this definition, e.g. by repeatedly doubling the previous definition. This has been corrected in KaTeX v0.16.10, where every expanded token in an `\\edef` counts as an expansion.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue or security advisory in the [KaTeX repository](https://github.com/KaTeX/KaTeX/)\n* Email us at [katex-security@mit.edu](mailto:katex-security@mit.edu)","published":"2024-03-25T19:40:00.843Z","modified":"2026-08-12T03:51:29.109552651Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"katex","fixedVersion":"0.16.10"}],"fix":{"url":"https://github.com/KaTeX/KaTeX/commit/e88b4c357f978b1bca8edfe3297f0aa309bcbe34","label":"KaTeX/KaTeX@e88b4c3"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/28xxx/CVE-2024-28243.json"},{"type":"ADVISORY","url":"https://github.com/KaTeX/KaTeX/security/advisories/GHSA-64fm-8hw2-v72w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-28243"},{"type":"FIX","url":"https://github.com/KaTeX/KaTeX/commit/e88b4c357f978b1bca8edfe3297f0aa309bcbe34"},{"type":"FIX","url":"https://github.com/github/advisory-database/pull/6777"},{"type":"PACKAGE","url":"https://github.com/KaTeX/KaTeX"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:29.109552651Z"}}