CVE-2026-84970 json
Heap over-read or silent misparse via 32-bit truncation of JSON length in BSON JSON parser
published 2026-09-03 2 mo ago modified 2026-09-10 59 d ago also EUVD-2026-70505
- cvss
- 6.2
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.1%
- EPSS 0.1% chance of exploitation in 30 days, percentile 2%
- public exploits
- 0
- none known
Summary
A numeric truncation weakness exists in the JSON parsing component of the MongoDB C++ Driver's BSON library. An actor who controls the text that an embedding application hands to the library's public JSON parsing interface, when that text is very large, can cause the library to read memory beyond the supplied buffer and return it to the caller, to silently accept only part of the input as a complete document, or to terminate the process. No MongoDB server, credentials, or non-default configuration is required; the effect is confined to the process that uses the library.
Patch / fix
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 2 mo ago
Exploit prediction
0.12% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 5.9 | CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N |
| CNA | 3.1 | 6.2 | CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H |
| CNA | 4.0 | 5.9 | CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:H/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 |
| NVD | 3.1 | 5.8 | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H |
Affected products
- MongoDB C++ Driver
Classification
- Weakness
-
- CWE-681 Incorrect Conversion between Numeric Types
References
-
jira.mongodb.org
/browse/CXX-3547
vendor-advisory, issue-tracking
Sources
- CVE List CVE-2026-84970
- NVD CVE-2026-84970
Fencer Vulns 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.