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VulnerabilityPublished

CVE-2026-126982: MongoDB C# Driver · Deserialization of Untrusted Data

Affects MongoDB C# DriverSource CVE Database V5

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Not known to be exploited · CVSS 7.7 High : upgrade to 3.14.0 soon.

Data as of 13 Nov 2026, 00:03 UTC

CVSS 4.0 base score
7.7High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (mongodb)CVSS 4.07.7
CNA (mongodb)CVSS 3.17.5
Patch
Available – fixed in 3.14.0
CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 12 Nov 2026.

What to do

Upgrade MongoDB C# Driver to 3.14.0.

Affected software

ProductAffectedFixed in
MongoDBC# DriverAffected
  • >=3.2.0 <3.14.0
Fixed in
  • 3.14.0

Description

A type allow-list bypass in the BSON serialization library of the MongoDB C# Driver allows a type-restriction check to be circumvented when polymorphic data is deserialized into loosely typed members. An unauthorized party who can supply or plant BSON/JSON data that the application later deserializes can cause the application process to instantiate .NET types outside the intended allow-list and populate them with unauthorized party-controlled values. In applications that contain a suitable gadget type, this can lead to arbitrary code execution in the context of the application, with corresponding loss of confidentiality, integrity, and availability. No special privileges beyond the ability to introduce data the application reads are required.

References

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