{"id":"CVE-2026-6691","summary":"MongoDB C Driver Cyrus SASL Canonicalization Buffer Overflow","details":"The MongoDB C Driver's Cyrus SASL integration performs unsafe string copying during username canonicalization, enabling a heap buffer overflow before any authentication or network traffic. This may be triggered by passing untrusted input in the username of a MongoDB URI with authMechanism=GSSAPI.","modified":"2026-07-08T08:11:37.186958467Z","published":"2026-05-06T15:08:23.671Z","database_specific":{"cwe_ids":["CWE-120"],"unresolved_ranges":[{"extracted_events":[{"introduced":"2.1.0"},{"last_affected":"2.1.2"}],"source":"AFFECTED_FIELD"}],"cna_assigner":"mongodb","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6691.json"},"references":[{"type":"WEB","url":"https://jira.mongodb.org/browse/CDRIVER-6134"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6691.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6691"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mongodb/mongo-c-driver","events":[{"introduced":"163250d2cc81c532a6315f6ad7e01bf35da9401d"},{"fixed":"81c27ddadd54e80d9743dee0e8b7a0a862aa6ab5"}],"database_specific":{"extracted_events":[{"introduced":"2.1.0"},{"fixed":"2.1.2"}],"source":"CPE_RANGE","cpe":"cpe:2.3:a:mongodb:c_driver:*:*:*:*:*:mongodb:*:*"}}],"versions":["2.1.1","2.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-6691.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}]}