{"id":"CVE-2026-96749","aliases":["GHSA-v4x9-3549-crwv","PYSEC-2026-4296"],"url":"https://o3.security/vulnerability/CVE-2026-96749","summary":"Heap out-of-bounds write via signed size overflow in BSON document encoding","details":"An integer overflow in the BSON document encoding component of the MongoDB Python Driver's bundled native extension may occur when a single document is built from an unusually large amount of caller-supplied data. Size arithmetic is performed in a signed 32-bit type, and the guard meant to catch the overflow is written in a form whose behavior is not defined by the C language standard. A party with no privileges who can place a very large value into data that an application encodes may, depending on how the native extension was built, cause a write outside the bounds of an allocated buffer inside the application's own process.","published":"2026-09-24T18:18:13.077Z","modified":"2026-10-21T10:55:57.152223054Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"pymongo","fixedVersion":"4.18.2"}],"fix":{"url":"https://github.com/mongodb/mongo-python-driver/pull/3066","label":"mongodb/mongo-python-driver#3066"},"references":[{"type":"WEB","url":"https://github.com/mongodb/mongo-python-driver/blob/4.18.2/doc/changelog.rst"},{"type":"WEB","url":"https://github.com/mongodb/mongo-python-driver/releases/tag/4.18.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/96xxx/CVE-2026-96749.json"},{"type":"ADVISORY","url":"https://github.com/mongodb/mongo-python-driver/security/advisories/GHSA-v4x9-3549-crwv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-96749"},{"type":"WEB","url":"https://github.com/mongodb/mongo-python-driver/pull/3066"},{"type":"WEB","url":"https://github.com/mongodb/mongo-python-driver/commit/640dd2383a1a2fb1a10e5222d50ebc0b22a61bd7"},{"type":"WEB","url":"https://github.com/mongodb/mongo-python-driver/commit/6ab44be0e97c9d1d5a23725c4978fb25f3249485"},{"type":"PACKAGE","url":"https://github.com/mongodb/mongo-python-driver"},{"type":"WEB","url":"https://www.mongodb.com/community/forums/t/pymongo-4-18-2-released/343732"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T10:55:57.152223054Z"}}