Vulnerability · Published Sep 24, 2026 · Assigned by mongodb
CVE-2026-96748Connection redirection via percent-encoded delimiter injection in connection string hosts
Medium 6.5
In plain English
A medium-severity security flaw in Python Driver from MongoDB. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 30% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
PyMongo's connection string parsing decodes percent-encoded characters in the host portion before the host list is separated on its delimiters. When an application places a hostname value supplied by an unauthenticated party into a connection string, that party may cause additional servers of their choosing to be added to the application's database client. The application may then send its authentication exchange and database operations to one of those servers, which can observe limited information and return altered results.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | pymongo | no fix listed | DEBIAN-CVE-2026-96748 |
| Debian:13 | pymongo | no fix listed | DEBIAN-CVE-2026-96748 |
| Debian:14 | pymongo | 4.18.2-1 | DEBIAN-CVE-2026-96748 |
| PyPI | pymongo | 4.18.2 | GHSA-vp6j-j7w5-5xjj |
| PyPI | pymongo | 4.18.2 | PYSEC-2026-4297 |
| Ubuntu:22.04:LTS | pymongo | no fix listed | UBUNTU-CVE-2026-96748 |
| Ubuntu:24.04:LTS | pymongo | no fix listed | UBUNTU-CVE-2026-96748 |
| Ubuntu:26.04:LTS | pymongo | no fix listed | UBUNTU-CVE-2026-96748 |
| Ubuntu:26.10 | pymongo | no fix listed | UBUNTU-CVE-2026-96748 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| MongoDB | Python Driver | 0 – before 4.18.2 |
Weakness: CWE-177 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N