CVE-2026-81529: Improper neutralization of delimiters in connection-URL construction allows connection-option injection in the

Routine

HIGH 7.1UPGRADE

CVE-2026-81529 is a high-severity flaw (CVSS 7.1) affecting c\# driver. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper neutralization of delimiters in connection-URL construction allows connection-option injection in the MongoDB C# Driver. When an application passes untrusted text into the driver's connection-URL builder and round-trips the builder back into a client configuration, the untrusted text is serialized without neutralizing the URL/option delimiters and is then re-parsed as authoritative connection options. A low-privileged user of such an app

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.1 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 79%)
CISA exploited list	No
Weakness	CWE-88
Published	2026-08-27
Last modified	2026-09-29

Publisher (CNA): MongoDB, Inc. · Vendor: mongodb

Last updated 2026-09-29 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-27 20:18 UTCPublished CVE record published
2026-09-29 19:16 UTCUpdated Record last modified

mongodb c\# driver UPGRADE

Affected: >= 2.10.0 and < 3.11.1

Fixed in: 3.11.1

Safe to downgrade to: a release before 2.10.0

1. Check installed version

apt-cache policy c-driver || rpm -q c-driver || c-driver --version

2. UPGRADE to 3.11.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade c-driver

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade c-driver

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.10.0 (Debian / Ubuntu)

apt-cache madison c-driver sudo apt install c-driver=<VERSION_BEFORE_2.10.0> sudo apt-mark hold c-driver

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list c-driver sudo dnf downgrade c-driver-<VERSION_BEFORE_2.10.0> sudo dnf versionlock add c-driver

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-81529?

c\# driver: upgrade to 3.11.1. Exact commands for each OS are on this page.

Is CVE-2026-81529 being exploited?

CVE-2026-81529 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-81529 affect?

CVE-2026-81529 affects c\# driver. Severity is high (CVSS 7.1). Improper neutralization of delimiters in connection-URL construction allows connection-option injection in the MongoDB C# Driver. When an application passes untrusted text into the driver's connection-URL builder and round-trips the builder

How urgent is CVE-2026-81529?

Priority 30/100. High severity

Software pages

MongoDB vulnerabilities

Related CVEs

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References

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