CVE-2026-88026: Regular expression injection via unescaped characters in LINQ query translation in MongoDB C# Driver

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-10 · updated 2026-09-29
Weakness: CWE-943

Description

Improper neutralization of regular-expression metacharacters in the LINQ query translation component of the MongoDB C# Driver can cause a caller-supplied character sequence to alter a regular-expression predicate generated by an affected application. An authenticated user who can influence such a value may cause the application to return records beyond those intended by the original filter.

Affected products

MongoDB Inc MongoDB .NET/C# Driver: from 2.14.0 before 3.11.2 — fixed in 3.11.2

How to fix

Upgrade to a fixed version: MongoDB Inc MongoDB .NET/C# Driver 3.11.2. Check the vendor advisory for mitigations.

References

https://jira.mongodb.org/browse/CSHARP-6177

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