CVE-2026-93394: medium-severity vulnerability in MongoDB Inc. C Driver
libmongoc SCRAM client nonce-validation bypass
Published · Updated
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.3epss 0.3%
A flaw in libmongoc's SCRAM authentication implementation caused the client to continue the authentication handshake and transmit the client proof even when a nonce mismatch was detected in the server's first message. An unauthorized party with a man-in-the-middle position could exploit this by injecting a crafted server-first-message containing a controlled salt and low iteration count, then capturing the resulting client proof to perform offline password cracking. This vulnerability is mitigated by TLS, which is standard in production deployments.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Affected products
MongoDB Inc. · C DriverRelated CVEs — MongoDB Inc. C Driver
In the same product, most dangerous first.
CVE-2026-93393CRITICALHeap overflow via oversized decrypted TLS record sequence in Windows Secure Channel streamEPSS 0.5%CVE-2026-93395MEDIUMInteger Underflow → Heap Out-of-Bounds Read in `bson_new_from_buffer()EPSS 0.4%CVE-2026-6231MEDIUMbson_validate may skip validation when processing certain inputsEPSS 0.2%