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CVE-2026-33215: NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system

37
Routine
MEDIUM 6.5REMOTEWATCHLISTUPGRADE

CVE-2026-33215 is a medium-severity flaw (CVSS 6.5) affecting nats-server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server provides an MQTT client interface. Prior to versions 2.11.15 and 2.12.5, Sessions and Messages can by hijacked via MQTT Client ID malfeasance. Versions 2.11.15 and 2.12.5 patch the issue. No known workarounds are available.

Why this priority

  • Remotely exploitable, no login, no user action
  • On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score6.5 (Medium)
Attack vectorNetwork (remote)
Attack complexityHigh
Privileges neededNone
User interactionNone
EPSS exploit chance0.2% (top 84%)
CISA exploited listNo
WeaknessCWE-287, CWE-488
Published2026-03-24
Last modified2026-06-17
Publisher (CNA): GitHub, Inc. · Vendor: linuxfoundation

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Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

linuxfoundation nats-server UPGRADE
Affected: >= 2.0.0 and < 2.11.15 · >= 2.12.0 and < 2.12.5
Fixed in: 2.11.15, 2.12.5
Safe to downgrade to: a release before 2.0.0
1. Check installed version
apt-cache policy nats-server || rpm -q nats-server || nats-server --version
2. UPGRADE to 2.11.15 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade nats-server
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade nats-server
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 2.0.0 (Debian / Ubuntu)
apt-cache madison nats-server sudo apt install nats-server=<VERSION_BEFORE_2.0.0> sudo apt-mark hold nats-server
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list nats-server sudo dnf downgrade nats-server-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add nats-server
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-2026-33215?

nats-server: upgrade to 2.11.15, 2.12.5. Exact commands for each OS are on this page.

Is CVE-2026-33215 being exploited?

CVE-2026-33215 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-2026-33215 affect?

CVE-2026-33215 affects nats-server. Severity is medium (CVSS 6.5). NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server provides an MQTT client interface. Prior to versions 2.11.15 and 2.12.5, Sessions and Messages can by hijacked via MQTT Client I

How urgent is CVE-2026-33215?

Priority 37/100. Remotely exploitable, no login, no user action; On your watchlist

Related CVEs

References

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