{"id":"GHSA-64fm-8hw2-v72w","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)","aliases":["CVE-2024-28243"],"modified":"2026-02-05T15:31:10.056078Z","published":"2024-03-25T19:38:18Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2024-03-25T19:38:18Z","nvd_published_at":"2024-03-25T20:15:07Z","cwe_ids":["CWE-606","CWE-674"],"severity":"MODERATE"},"references":[{"type":"WEB","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":"WEB","url":"https://github.com/github/advisory-database/pull/6777"},{"type":"WEB","url":"https://github.com/KaTeX/KaTeX/commit/e88b4c357f978b1bca8edfe3297f0aa309bcbe34"},{"type":"PACKAGE","url":"https://github.com/KaTeX/KaTeX"}],"affected":[{"package":{"name":"katex","ecosystem":"npm","purl":"pkg:npm/katex"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.12.0"},{"fixed":"0.16.10"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2024/03/GHSA-64fm-8hw2-v72w/GHSA-64fm-8hw2-v72w.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}