CVE-2026-81527
MEDIUMDescription
A NoSQL/expression injection weakness exists in the LINQ-to-aggregation query translation layer of the MongoDB C# Driver, in both aggregation expression and query filter translation. When application-supplied values are embedded in certain query constructs, special elements contained within those values are not properly escaped before the resulting query is transmitted to the database, so portions of the value may be interpreted by the database as query logic rather than as data. A user able to supply values that an application incorporates into an affected query may thereby cause unintended data to be returned or query results to be altered.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 22% of all known CVEs.
References
Related Vulnerabilities
Other CWE-943 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2017-12904 | High | 8.8 | 6.4% | - | Fix |
| CVE-2026-27886 | High | 7.5 | 2.5% | - | Fix |
| CVE-2020-36195 | Critical | 9.8 | 1.8% | - | Fix |
| CVE-2018-7829 | High | 8.8 | 1.7% | - | Fix |
| CVE-2022-36084 | Critical | 9.9 | 1.5% | - | Fix |
| CVE-2021-1349 | Medium | 6.5 | 1.4% | - | Fix |
Common questions
How do I fix CVE-2026-81527?
Upgrade c\# driver to 3.11.1 or later.
Is CVE-2026-81527 being actively exploited?
Not that we know of. CVE-2026-81527 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.31% is the estimated probability that it will be exploited in the next 30 days. That is higher than 22% of all scored CVEs.
How severe is CVE-2026-81527?
CVE-2026-81527 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-81527 affect?
Published advisories record a fix for c\# driver (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-29.