CVE-2026-42154: Prometheus is an open-source monitoring system and time series database

This month

HIGH 7.5REMOTEUPGRADE

CVE-2026-42154 is a high-severity flaw (CVSS 7.5) affecting prometheus. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Prometheus is an open-source monitoring system and time series database. Prior to versions 3.5.3 and 3.11.3, the remote read endpoint (/api/v1/read) does not validate the declared decoded length in a snappy-compressed request body before allocating memory. An unauthenticated attacker can send a small payload that causes a huge heap allocation per request. Under concurrent load this can exhaust available memory and crash the Prometheus process. Th

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 43%)
CISA exploited list	No
Weakness	CWE-400, CWE-789, CWE-770
Published	2026-05-04
Last modified	2026-09-10

Publisher (CNA): GitHub, Inc. · Vendor: prometheus

Last updated 2026-09-10 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-04 19:16 UTCPublished CVE record published
2026-09-10 13:20 UTCUpdated Record last modified

prometheus prometheus UPGRADE

Affected: < 3.5.3 · >= 3.6.0 and < 3.11.3

Fixed in: 3.5.3, 3.11.3

Safe to downgrade to: a release before 3.6.0

1. Check installed version

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

2. UPGRADE to 3.5.3 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade prometheus

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 3.6.0 (Debian / Ubuntu)

apt-cache madison prometheus sudo apt install prometheus=<VERSION_BEFORE_3.6.0> sudo apt-mark hold prometheus

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

dnf --showduplicates list prometheus sudo dnf downgrade prometheus-<VERSION_BEFORE_3.6.0> sudo dnf versionlock add prometheus

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-2026-42154?

prometheus: upgrade to 3.5.3, 3.11.3. Exact commands for each OS are on this page.

Is CVE-2026-42154 being exploited?

CVE-2026-42154 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-2026-42154 affect?

CVE-2026-42154 affects prometheus. Severity is high (CVSS 7.5). Prometheus is an open-source monitoring system and time series database. Prior to versions 3.5.3 and 3.11.3, the remote read endpoint (/api/v1/read) does not validate the declared decoded length in a snappy-compressed request body before al

How urgent is CVE-2026-42154?

Priority 45/100. High severity; Remotely exploitable, no login, no user action

Software pages

Prometheus vulnerabilities

Related CVEs

CVE-2026-42151 HIGH 7.5 UPGRADE Prometheus is an open-source monitoring system and time series database
CVE-2026-44903 MEDIUM 6.1 UPGRADE Prometheus is an open-source monitoring system and time series database
CVE-2026-40179 MEDIUM 6.1 UPGRADE Prometheus is an open-source monitoring system and time series database

References

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