CVE-2026-6811: Stack exhaustion vulnerability in the MongoDB PHP driver can cause application crashes when processing deeply

Routine

MEDIUM 5.9REMOTEUPGRADE

CVE-2026-6811 is a medium-severity flaw (CVSS 5.9) affecting php driver. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Stack exhaustion vulnerability in the MongoDB PHP driver can cause application crashes when processing deeply nested BSON documents in unusual circumstances when the source of these BSON documents is not MongoDB Server.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 70%)
CISA exploited list	No
Weakness	CWE-674
Published	2026-05-14
Last modified	2026-10-26

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

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-14 22:16 UTCPublished CVE record published
2026-10-26 14:10 UTCUpdated Record last modified

mongodb php driver UPGRADE

Affected: >= 1.21.0 and < 1.21.5 · >= 2.1.0 and < 2.1.8

Fixed in: 1.21.5, 2.1.8

Safe to downgrade to: a release before 1.21.0

1. Check installed version

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

2. UPGRADE to 1.21.5 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade php-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 1.21.0 (Debian / Ubuntu)

apt-cache madison php-driver sudo apt install php-driver=<VERSION_BEFORE_1.21.0> sudo apt-mark hold php-driver

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

dnf --showduplicates list php-driver sudo dnf downgrade php-driver-<VERSION_BEFORE_1.21.0> sudo dnf versionlock add php-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-2026-6811?

php driver: upgrade to 1.21.5, 2.1.8. Exact commands for each OS are on this page.

Is CVE-2026-6811 being exploited?

CVE-2026-6811 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-2026-6811 affect?

CVE-2026-6811 affects php driver. Severity is medium (CVSS 5.9). Stack exhaustion vulnerability in the MongoDB PHP driver can cause application crashes when processing deeply nested BSON documents in unusual circumstances when the source of these BSON documents is not MongoDB Server.

How urgent is CVE-2026-6811?

Priority 33/100. Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities · MongoDB vulnerabilities

Related CVEs

CVE-2026-106436 MEDIUM 4.8 UPGRADE The BSON encoder in the MongoDB PHP Driver does not check some return values after a document exceeds libbson'
CVE-2026-106432 LOW 3.6 UPGRADE The BSON encoder in the MongoDB PHP Driver converts a string length to a 32-bit value without validation

References

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