{"id":"UBUNTU-CVE-2025-62496","details":"A vulnerability exists in the QuickJS engine's BigInt string parsing logic (js_bigint_from_string) when attempting to create a BigInt from a string with an excessively large number of digits. The function calculates the necessary number of bits (n_bits) required to store the BigInt using the formula: $$\\text{n\\_bits} = (\\text{n\\_digits} \\times 27 + 7) / 8 \\quad (\\text{for radix 10})$$   *  For large input strings (e.g., $79,536,432$ digits or more for base 10), the intermediate calculation $(\\text{n\\_digits} \\times 27 + 7)$ exceeds the maximum value of a standard signed 32-bit integer, resulting in an Integer Overflow.   *  The resulting n_bits value becomes unexpectedly small or even negative due to this wrap-around.   *  This flawed n_bits is then used to compute n_limbs, the number of memory \"limbs\" needed for the BigInt object. Since n_bits is too small, the calculated n_limbs is also significantly underestimated.   *  The function proceeds to allocate a JSBigInt object using this underestimated n_limbs.   *  When the function later attempts to write the actual BigInt data into the allocated object, the small buffer size is quickly exceeded, leading to a Heap Out-of-Bounds Write as data is written past the end of the allocated r-\u003etab array.","modified":"2026-05-20T16:23:39.952604836Z","published":"2025-10-16T16:15:00Z","upstream":["CVE-2025-62496"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2025-62496"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2025-62496"},{"type":"REPORT","url":"https://issuetracker.google.com/434193016"},{"type":"REPORT","url":"https://bellard.org/quickjs/Changelog"}],"affected":[{"package":{"name":"quickjs","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/quickjs?arch=source&distro=esm-apps%2Fnoble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2021.03.27-1","2021.03.27-1ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_version":"2021.03.27-1ubuntu0.1~esm1","binary_name":"libquickjs"},{"binary_name":"quickjs","binary_version":"2021.03.27-1ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-62496.json"}},{"package":{"name":"quickjs","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/quickjs?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2024.01.13-5","2025.04.26-1"],"ecosystem_specific":{"binaries":[{"binary_name":"libquickjs","binary_version":"2025.04.26-1"},{"binary_name":"quickjs","binary_version":"2025.04.26-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-62496.json"}},{"package":{"name":"quickjs","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/quickjs?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2025.04.26-1","2025.04.26-1build1"],"ecosystem_specific":{"binaries":[{"binary_name":"libquickjs","binary_version":"2025.04.26-1build1"},{"binary_name":"quickjs","binary_version":"2025.04.26-1build1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-62496.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:A/AC:H/AT:P/PR:L/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},{"type":"Ubuntu","score":"medium"}]}