CVE-2025-27821VulnerabilityPublished 26 Jan 2026

CVE-2025-27821: Apache Software Foundation HDFS native client · Out-of-bounds Write

Affects Apache Software Foundation HDFS native clientSource CVE Database V5

Not known to be exploited · CVSS 7.3 High : upgrade to 3.4.2 soon.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

7.3High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.9% chance of exploitation in 30 days – higher than 59% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.4.2

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 26 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade HDFS native client and Apache Software Foundation/org.apache.hadoop:hadoop-hdfs-native-client to 3.4.2.

Affected software

Product	Affected	Fixed in
Apache Software FoundationHDFS native client	Affected >=3.2.0 <3.4.2	Fixed in 3.4.2
MavenApache Software Foundation/org.apache.hadoop:hadoop-hdfs-native-client`pkg:maven/Apache Software Foundation/org.apache.hadoop:hadoop-hdfs-native-client`Other threats	Affected >=3.2.0 <3.4.2	Fixed in 3.4.2
Mavenorg.apache.hadoop/hadoop-hdfs-native-client`pkg:maven/org.apache.hadoop/hadoop-hdfs-native-client`Other threats	Affected =3.2.0	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate this vulnerability, organizations should promptly upgrade all affected Apache Hadoop HDFS native client installations to version 3.4.2 or later, where the issue is resolved. Beyond patching, it is advisable to implement network segmentation to restrict access to Hadoop services, limiting exposure to untrusted networks. Monitoring and logging of HDFS client interactions should be enhanced to detect anomalous behavior indicative of exploitation attempts. Employing runtime memory protection mechanisms such as Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP) can reduce exploitation success. Additionally, organizations should conduct thorough security assessments of their big data environments, ensuring that only authorized users and systems can interact with Hadoop components. Regular vulnerability scanning and penetration testing focused on big data infrastructure can help identify residual risks. Finally, maintaining an incident response plan tailored to big data platform compromises will improve readiness in case of exploitation.

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.

Impact

For European organizations, the impact of CVE-2025-27821 could be substantial, especially for those heavily reliant on Hadoop ecosystems for big data processing, analytics, and storage. Successful exploitation could compromise the confidentiality of sensitive data by enabling unauthorized code execution or data manipulation. Integrity could be undermined through corrupted data or altered processing results, while availability might be affected by crashes or denial-of-service conditions triggered by memory corruption. Given the widespread use of Hadoop in sectors such as finance, telecommunications, healthcare, and government, the vulnerability poses a risk to critical infrastructure and services. Additionally, the absence of authentication requirements means attackers could exploit this vulnerability remotely if they can interact with the HDFS native client, increasing the attack surface. The threat is amplified in environments where Hadoop clusters are exposed or insufficiently segmented from untrusted networks.

CWE-787Out-of-bounds Write (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #5
The product writes data past the end, or before the beginning, of the intended buffer.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Operation · Build and Compilation · Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Jan 2026, 10:05 UTC

WeaknessesCWE-787

Technical details

References

Community reviews

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