MongoDBGHSA-fqmh-x7gg-pfgw
Heap overflow via truncated base64 encoding of binary fields in length-limited JSON output
Medium6.3CVE-2026-84969 · Published Sep 3, 2026
### Impact A memory-handling error in the BSON-to-JSON conversion helpers of the MongoDB C Driver can write a small number of bytes past the end of a heap buffer when a binary field is encoded and the output is cut short at a caller-configured length limit. A party who supplies the document content, with no privileges on the application that links the driver, may cause a small amount of data outside the intended buffer to be altered. ### Patches Fixed in 1.30.9 and 2.5.2 ### Workarounds Disable logging or logging truncation. ### References https://jira.mongodb.org/browse/CDRIVER-6410
Affected versions
| Package | Affected | Fixed in |
|---|---|---|
| MongoDB C Driver Product | >= 1.30.0, < 1.30.9 | 1.30.9 |
| >= 2.0.0, < 2.5.2 | 2.5.2 |
Details and references
- CVSS 4.0
- CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- Severity from
- GitHub (reviewed advisory)
More MongoDB advisories
All MongoDB| Date | Advisory | Severity | Fixed in |
|---|---|---|---|
| Sep 3 | Authenticated KMS request forgery via CRLF injection in GCP key identifier strings | Medium5.7 | 1.20.2 |
| Sep 3 | Heap out-of-bounds read via corrupt nested BSON in field path error message | Medium6.9 | 1.21.8+2 more |
| Sep 3 | Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path | High7.1 | 1.20.4 |
| Sep 3 | BSON element injection via NUL-embedded document keys in builder append | Medium5.9 | 4.5.2 |
| Sep 3 | Heap over-read or silent misparse via 32-bit truncation of JSON length in BSON JSON parser | Medium5.9 | 4.5.2 |
| Sep 3 | MongoDB for VS Code: command injection | Medium5.1 | 1.17.1 |