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Fencer Intel
medium 6.5

CVE-2026-114654 json

BSON output corruption via out-of-range binary subtype bypassing UUID and OldBinary guards

published 18d ago modified 10d ago also EUVD-2026-108328

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

A numeric-type conversion flaw in the BSON handling library of the MongoDB C# Driver allows an out-of-range binary subtype value supplied through untrusted textual input to bypass the library's binary-element integrity checks. When such a value is later encoded, it is narrowed to a smaller wire representation, producing binary elements that misdeclare their type or length. An unauthenticated party able to supply text parsed by an affected application can cause it to emit and persist malformed binary data, which subsequent readers either reject with an error or silently interpret as shorter than the data that was validated.

Patch / fix

  • MongoDB C# Driver 3.13.0

Is CVE-2026-114654 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
10d ago

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/mongodb/mongo-csharp-driver/security/advisories/GHSA-5h2q-6c9r-7x25 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • MongoDB C# Driver

Classification

Weakness
  • CWE-681 Incorrect Conversion between Numeric Types

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.