CVE-2026-96749 Heap out-of-bounds write via signed size overflow in BSON document encoding
An integer overflow in the MongoDB Python Driver's BSON encoding allows unprivileged attackers to trigger out-of-bounds writes, potentially leading to code execution or crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-96749?
CVE-2026-96749 is a high-severity vulnerability in MongoDB Python Driver, published on 24 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
An integer overflow in the BSON document encoding component of the MongoDB Python Driver's bundled native extension may occur when a single document is built from an unusually large amount of caller-supplied data. Size arithmetic is performed in a signed 32-bit type, and the guard meant to catch the overflow is written in a form whose behavior is not defined by the C language standard. A party with no privileges who can place a very large value into data that an application encodes may, depending on how the native extension was built, cause a write outside the bounds of an allocated buffer inside the application's own process.
Weakness: CWE-190
Which versions are affected by CVE-2026-96749?
3 open source packages ship an affected version, including pymongo.
| Package | Affected | Fixed in |
|---|---|---|
pymongo PyPI | All versions | 4.18.2 |
pymongo PyPI | All versions | 4.18.2 |
pymongo PyPI | All versions | 4.18.2 |
How do I fix CVE-2026-96749?
Upgrade pymongo to 4.18.2 or later.
Is CVE-2026-96749 being exploited?
There is no known exploitation of CVE-2026-96749 in the wild and no public exploit code.
Sources
Also known as AZL-105110, DEBIAN-CVE-2026-96749, ECHO-edca-11e2-60b0, GHSA-v4x9-3549-crwv, MINI-vcrv-gmw5-45rr, PYSEC-2026-4296 and 2 more.