MuJS 1.3.6 before 1.3.9 contains a heap out-of-bounds read and write vulnerability in Array.prototype.sort that allows attackers to corrupt memory by inflating a simple array's length. Attackers can supply JavaScript that enlarges a dense array's length and calls sort, causing Ap_sort_cmp and Ap_sort_swap to access slots past the buffer and crash the process.
https://hackmd.io/@haind-pwn/mujs-array-length-flat-oob
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-101138
https://codeberg.org/ccxvii/mujs/src/commit/307f18c4216420f2f56e22d8e7040baa39a6304a/jsarray.c#L245
https://codeberg.org/ccxvii/mujs/commit/32064e10caa45e68fc87331ca53d042049cc9396
Published: 2026-10-14
Updated: 2026-10-15
Base Score: 5.6
Vector: CVSS2#AV:L/AC:L/Au:N/C:N/I:P/A:C
Severity: Medium
Base Score: 6.1
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
Severity: Medium
Base Score: 6.9
Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
Severity: Medium
EPSS: 0.00172