Heap overflow via truncated binary-field base64 encoding
Published Sep 3, 2026 · Updated Sep 3, 2026
Out-of-bounds write in MongoDB C Driver 1.30.0 through 1.30.8 and 2.0.0 through 2.5.1 allows remote attackers to alter heap data. The BSON-to-JSON conversion helpers truncate base64 output at a caller-configured length but still write encoded bytes past the allocated heap buffer. Reachability requires an application to convert an attacker-supplied document containing a binary field with the limiting API; the bounded reported consequence is corruption of adjacent heap data.
Summary
What happened
Out-of-bounds write in MongoDB C Driver 1.30.0 through 1.30.8 and 2.0.0 through 2.5.1 allows remote attackers to alter heap data. The BSON-to-JSON conversion helpers truncate base64 output at a caller-configured length but still write encoded bytes past the allocated heap buffer. Reachability requires an application to convert an attacker-supplied document containing a binary field with the limiting API; the bounded reported consequence is corruption of adjacent heap data.
The record
- CVE
- CVE-2026-84969
- Published
- Sep 3, 2026
- Updated
- Sep 3, 2026
- Vendor
- MongoDB
- Product
- MongoDB C++ Driver
- Classifications
- CWE-787
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 3, 2026CVE publishedPublication date reported by the CVE source.
- Sep 3, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1.30.0 <1.30.9
- Affected versionversion=2.0.0 <2.5.2
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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