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CVE-2026-126839VulnerabilityPublished

Deserialization Type-restriction Control

Source GCVE Database

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Authoritative record:CVE-2026-126839· Low 2.3

Not known to be exploited · CVSS 2.3 Low : upgrade to 3.14.0 when convenient.

Data as of 13 Nov 2026, 01:10 UTC

CVSS 4.0 base score
2.3Low
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (mongodb)CVSS 4.02.3
CNA (mongodb)CVSS 3.14.2
Patch
Available – fixed in 3.14.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 12 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 C# Driver and mongodb.driver to 3.14.0.

Affected software

ProductAffectedFixed in
MongoDBC# DriverAffected
  • >=2.21.0 <3.14.0
Fixed in
  • 3.14.0
NuGetmongodb.driverpkg:nuget/mongodb.driverOther threatsAffected
  • >=2.21.0 <3.14.0
Fixed in
  • 3.14.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, applications should avoid deserializing untrusted BSON content into loosely typed members or implement additional validation to restrict deserialization to known safe types.

Description

A vulnerability in the BSON serialization component allows bypassing a type-restriction control due to an overly permissive heuristic used to identify compiler-generated types. This flaw enables an attacker who can supply BSON content to cause the deserialization of types outside the intended allow-list, potentially leading to unexpected object states and errors in application logic. Exploitation requires only the ability to influence the deserialization input and does not require elevated privileges.

References

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