What is CVE-2025-27821?

CVE-2025-27821 is a high-severity vulnerability in Apache Hadoop, classified under Out-of-bounds Write. CVSS score: 7.3/10. Published 2026-01-26.

How severe is CVE-2025-27821?

High severity. CVSS v3 base score is 7.3 out of 10.

Buffer overflow in Apache Hadoop

CVE-2025-27821

Out-of-bounds Write vulnerability in Apache Hadoop HDFS native client. This issue affects Apache Hadoop: from 3.2.0 before 3.4.2. Users are recommended to upgrade to version 3.4.2, which fixes the issue.

Vulnerability class: Buffer Overflow

Published 2026-01-26 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.010 (60.2th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 60th percentile — 60.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.010 · change: +0.001

Affected products

Apache Hadoop
Apache Software Foundation Hdfs Native Client — versions 3.2.0

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

lists.apache.org/thread/kwjhyyx0wl2z9b0mw0styjk0hhdbyplh (vendor-advisory, Mailing List, Vendor Advisory)
af854a3a-2127-422b-91ae-364da2661108 (Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2025-27821?: CVE-2025-27821 is a high-severity vulnerability in Apache Hadoop, classified under Out-of-bounds Write. CVSS score: 7.3/10. Published 2026-01-26.
How severe is CVE-2025-27821?: High severity. CVSS v3 base score is 7.3 out of 10.