CVE-2026-18687: MongoDB Server's handling of a Queryable Encryption maintenance operation did not properly validate certain re

Routine

HIGH 7.1UPGRADEDOWNGRADE

CVE-2026-18687 is a high-severity flaw (CVSS 7.1) affecting mongodb, mongodb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

MongoDB Server's handling of a Queryable Encryption maintenance operation did not properly validate certain request parameters against the collection's encrypted field configuration before use. An authenticated user with readWrite privileges could submit a specially formed request that leads to a server crash or excessive internal writes, resulting in resource exhaustion and corruption of encrypted index data.

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	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 86%)
CISA exploited list	No
Weakness	CWE-191
Published	2026-08-11
Last modified	2026-10-23

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

Am I affected?

Timeline

2026-08-11 19:17 UTCPublished CVE record published
2026-10-23 21:10 UTCUpdated Record last modified

mongodb mongodb UPGRADE

Affected: >= 8.0.0 and < 8.0.29 · >= 8.2.0 and <= 8.2.12 · >= 8.3.0 and < 8.3.8

Fixed in: 8.0.29, 8.3.8

Safe to downgrade to: a release before 8.0.0

1. Check installed version

apt-cache policy mongodb || rpm -q mongodb || mongodb --version

2. UPGRADE to 8.0.29 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mongodb

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mongodb

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 8.0.0 (Debian / Ubuntu)

apt-cache madison mongodb sudo apt install mongodb=<VERSION_BEFORE_8.0.0> sudo apt-mark hold mongodb

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

dnf --showduplicates list mongodb sudo dnf downgrade mongodb-<VERSION_BEFORE_8.0.0> sudo dnf versionlock add mongodb

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.

mongodb mongodb DOWNGRADE

Affected: 9.0.0 alpha0 · 9.0.0 alpha1 · 9.1.0 alpha0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0.0

1. Check installed version

apt-cache policy mongodb || rpm -q mongodb || mongodb --version

2. No fixed release: DOWNGRADE to a release before 9.0.0 (Debian / Ubuntu)

apt-cache madison mongodb sudo apt install mongodb=<VERSION_BEFORE_9.0.0> sudo apt-mark hold mongodb

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list mongodb sudo dnf downgrade mongodb-<VERSION_BEFORE_9.0.0> sudo dnf versionlock add mongodb

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-2026-18687?

mongodb: upgrade to 8.0.29, 8.3.8; mongodb: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-18687 being exploited?

CVE-2026-18687 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-2026-18687 affect?

CVE-2026-18687 affects mongodb, mongodb. Severity is high (CVSS 7.1). MongoDB Server's handling of a Queryable Encryption maintenance operation did not properly validate certain request parameters against the collection's encrypted field configuration before use. An authenticated user with readWrite privilege

How urgent is CVE-2026-18687?

Priority 28/100. High severity

Software pages

MongoDB vulnerabilities

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References

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