CVE-2025-27821 HDFS native client: Out of bounds write in URI parser of native HDFS client

What is CVE-2025-27821?

CVE-2025-27821 is a high-severity memory corruption vulnerability in Apache Software Foundation HDFS native client, published on 26 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-787

Which versions are affected by CVE-2025-27821?

2 open source packages ship an affected version, including org.apache.hadoop:hadoop-hdfs-native-client. It affects 1 product.

Products include Apache Hadoop.

How do I fix CVE-2025-27821?

Upgrade org.apache.hadoop:hadoop-hdfs-native-client to 3.4.2 or later.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2025-27821 being exploited?

There is no known exploitation of CVE-2025-27821 in the wild and no public exploit code.

Other vulnerabilities in Apache Software Foundation HDFS native client

• CVE-2022-25168 Command injection in org.apache.hadoop.fs.FileUtil.unTarUsingTar Critical 9.8
• CVE-2021-37404 Heap buffer overflow in libhdfs native library Critical 9.8
• CVE-2022-26612 Arbitrary file write in FileUtil#unpackEntries on Windows Critical 9.8
• CVE-2019-17195 Improper Check for Unusual or Exceptional Conditions in Connect2id Nimbus JOSE+JWT Critical 9.8
• CVE-2017-15718 Exposure of Sensitive Information in Hadoop Critical 9.8

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as CLEANSTART-2026-HK83205, GHSA-92cc-952p-v8rh.