CVE-2026-120954: medium-severity vulnerability in MongoDB C Driver
Silent element-count truncation via 32-bit bit-length overflow in packed-bit vector views
Published
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.3epss 0.2%
A weakness in the BSON library's handling of a specialized binary vector data type allows an arithmetic wraparound when computing the number of elements described by an oversized attacker-supplied value. On builds where the platform word size is 32 bits, an application that parses untrusted BSON data can be made to process only a small fraction of the supplied elements while the operation reports success, producing results that disagree with byte-oriented accessors and with 64-bit builds of the same library. No authentication or user interaction is required beyond getting the application to parse the data. The impact is limited to data integrity; memory safety is not affected and no information is disclosed.
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Affected products
MongoDB · C DriverRelated CVEs — MongoDB C Driver
In the same product, most dangerous first.
CVE-2026-96746HIGHHeap buffer overflow via mid-scan command list growth in client topology monitoringEPSS 0.4%CVE-2026-120678HIGHMongoDB C Driver leaks the decompressed reply buffer when an OP_COMPRESSED reply fails to parse (denial of service)EPSS 0.4%CVE-2026-120955HIGHMongoDB C Driver Modern GridFS mongoc_gridfs_bucket_download_to_stream() Aborts Application on Malformed GridFS MetadataEPSS 0.4%CVE-2026-120684MEDIUMMongoDB C Driver GridFS gap lets a shared writer recover a protected client's passwordEPSS 0.3%CVE-2026-84963MEDIUMSilent field truncation via unchecked int cast of huge JSON string values in JSON-to-BSON parserEPSS 0.3%CVE-2026-84969MEDIUMHeap overflow via truncated base64 encoding of binary fields in length-limited JSON outputEPSS 0.3%