BSON output corruption via out-of-range binary subtype in MongoDB C# Driver
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · Low
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
The MongoDB C# Driver contains a numeric type conversion flaw (CWE-681) in its BSON handling library, from version 2.0.0 before 3.13.0. An out-of-range binary subtype value supplied through untrusted text bypasses the binary element integrity checks. When the value is encoded, it is narrowed to a smaller representation, producing binary elements with wrong type or length declarations. An unauthenticated party who can supply text parsed by an affected application can cause it to persist malformed binary data, which readers either reject or read as shorter than the validated data.
Written with Claude Haiku 5.5 from the sources below · 2026-10-30
Description from the CNA
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
Upgrade MongoDB C# Driver to version 3.13.0, which fixes the flaw.
Written with Claude Haiku 5.5 from the sources below · 2026-10-30
- Fix · CNA C# Driver (MongoDB) Fixed in 3.13.0
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
MongoDB C# Driver 3.13.0
11 records Highest priority Priority HIGH 5 HIGH, 6 MEDIUM
Other records, highest priority first
- TI-2026-79424 NoSQL command injection via mismatched BSON length in MongoDB C# DriverPriority HIGH 70
- TI-2026-79422 Unbounded memory growth in MongoDB C# Driver BSON deserializationPriority HIGH 69
- TI-2026-79427 Authentication bypass via issuer-and-serial-only certificate equalityPriority HIGH 68
Timeline
- 2026-10-22 Threatist record created from CVE-2026-114654
- 2026-10-23 1 new reference · CNA
- 2026-10-23 Priority changed: MEDIUM → LOW
- 2026-10-30 CISA SSVC decision points changed
- 2026-10-30 Priority changed: LOW → HIGH
References
More MongoDB vulnerabilities
- TI-2019-08023 Code injection in mongo-express KEVCVSS 3.1CRITICAL 9.9
- TI-2025-13542 Zlib compressed protocol header length confusion may allow memory read KEVCVSS 4.0HIGH 8.7
- TI-2026-79424 NoSQL command injection via mismatched BSON length in MongoDB C# Driver CVSS 4.0MEDIUM 6.9
- TI-2026-79422 Unbounded memory growth in MongoDB C# Driver BSON deserialization CVSS 4.0HIGH 8.2
- TI-2026-79427 Authentication bypass via issuer-and-serial-only certificate equality CVSS 4.0HIGH 7.6
- TI-2026-79426 NoSQL injection in MongoDB C# Driver LINQ filter field names CVSS 4.0HIGH 7.2
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences