CVE-2025-27821: Out-of-bounds Write vulnerability in Apache Hadoop HDFS native client. This issue affects Apache Hadoop: from

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HIGH 7.3REMOTEWATCHLISTUPGRADE

CVE-2025-27821 is a high-severity flaw (CVSS 7.3) affecting hadoop. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.3 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-01-26
Last modified	2026-06-17

Publisher (CNA): Apache Software Foundation · Vendor: apache

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

Am I affected?

Timeline

2026-01-26 10:16 UTCPublished CVE record published
2026-06-17 09:04 UTCUpdated Record last modified

apache hadoop UPGRADE

Affected: >= 3.2.0 and < 3.4.2

Fixed in: 3.4.2

Safe to downgrade to: a release before 3.2.0

1. Check installed version

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

2. UPGRADE to 3.4.2 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade hadoop

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 3.2.0 (Debian / Ubuntu)

apt-cache madison hadoop sudo apt install hadoop=<VERSION_BEFORE_3.2.0> sudo apt-mark hold hadoop

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

dnf --showduplicates list hadoop sudo dnf downgrade hadoop-<VERSION_BEFORE_3.2.0> sudo dnf versionlock add hadoop

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-2025-27821?

hadoop: upgrade to 3.4.2. Exact commands for each OS are on this page.

Is CVE-2025-27821 being exploited?

CVE-2025-27821 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-2025-27821 affect?

CVE-2025-27821 affects hadoop. Severity is high (CVSS 7.3). 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.

How urgent is CVE-2025-27821?

Priority 50/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Apache Hadoop vulnerabilities

Related CVEs

CVE-2024-23454 MEDIUM 6.2 UPGRADE Apache Hadoop’s RunJar.run() does not set permissions for temporary directory by default

References

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