CVE-2026-42154

CVE-2026-42154 is a high-severity vulnerability in Prometheus with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Description

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. This issue has been patched in versions 3.5.3 and 3.11.3.

Frequently asked questions

What is CVE-2026-42154?
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. This issue has been patched in versions 3.5.3 and 3.11.3.
How severe is CVE-2026-42154?
CVE-2026-42154 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-42154 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42154?
CVE-2026-42154 affects Prometheus. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-42154?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-42154 have an EU (EUVD) identifier?
Yes. CVE-2026-42154 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-27091.
When was CVE-2026-42154 published?
CVE-2026-42154 was published on 2026-05-04 and last updated on 2026-07-07.

References

Affected products (1)

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