CVE-2025-27821
Published: 26 January 2026
Summary
CVE-2025-27821 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Apache Hadoop. Its CVSS base score is 7.3 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 14.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 CM-2 (Baseline Configuration) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2025-27821 is an out-of-bounds write vulnerability (CWE-787) in the Apache Hadoop HDFS native client. It affects Apache Hadoop versions from 3.2.0 up to but not including 3.4.2. The issue was published on 2026-01-26 and carries a CVSS v3.1 base score of 7.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L), indicating high severity due to its network accessibility and lack of prerequisites for exploitation.
Unauthenticated attackers with network access to a vulnerable Hadoop instance can exploit this flaw remotely with low complexity and no user interaction required. Successful exploitation allows limited impacts: low confidentiality (partial data exposure), low integrity (minor unauthorized modifications), and low availability (limited denial of service), all within the unchanged scope of the affected component.
Apache advisories recommend upgrading to version 3.4.2, which resolves the vulnerability. Detailed discussions appear in the Apache mailing list thread at https://lists.apache.org/thread/kwjhyyx0wl2z9b0mw0styjk0hhdbyplh and the oss-security announcement at http://www.openwall.com/lists/oss-security/2026/01/23/7.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-206351
Vulnerability details
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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Out-of-bounds write in network-accessible HDFS native client directly enables remote exploitation of a public-facing Hadoop service without authentication.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely remediation of known flaws such as this out-of-bounds write by applying the vendor-supplied upgrade to Hadoop 3.4.2.
Establishes and maintains approved baseline configurations that exclude vulnerable Hadoop versions (3.2.0–3.4.1) from operational use.
Requires ongoing vulnerability scanning to discover instances of the affected HDFS native client before exploitation occurs.