CVE-2021-35561Network attack vector

Denial of service via deserialized load factor

Published Oct 20, 2021 · Updated Sep 25, 2024

Deserialization flaw in Oracle Java SE 7u311, 8u301, 11.0.12, and 17 allows remote attackers to exhaust memory and interrupt service. HashMap.readObject and HashSet.readObject retain an out-of-range load factor from a serialized stream, enabling excessive allocation during reconstruction. Exposure requires untrusted serialized data to reach these Utility APIs, including through a web service or sandboxed Java code, and can terminate the affected application with an out-of-memory condition.

CVSS severity5.3
Medium
EPSS probability6.95%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Deserialization flaw in Oracle Java SE 7u311, 8u301, 11.0.12, and 17 allows remote attackers to exhaust memory and interrupt service. HashMap.readObject and HashSet.readObject retain an out-of-range load factor from a serialized stream, enabling excessive allocation during reconstruction. Exposure requires untrusted serialized data to reach these Utility APIs, including through a web service or sandboxed Java code, and can terminate the affected application with an out-of-memory condition.

The record

CVE
CVE-2021-35561
Published
Oct 20, 2021
Updated
Sep 25, 2024
Vendor
Oracle Corporation
Product
Java Platform, Standard Edition (Java SE)
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 25, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Java SE:11.0.12
  2. Affected versionversion=Java SE:17
  3. Affected versionversion=Java SE:7u311
  4. Affected versionversion=Java SE:8u301
  5. Affected versionversion=Oracle GraalVM Enterprise Edition:20.3.3
  6. Affected versionversion=Oracle GraalVM Enterprise Edition:21.2.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Oracle Corporation · Java Platform, Standard Edition (Java SE)version=Java SE:11.0.12; version=Java SE:17; version=Java SE:7u311; version=Java SE:8u301; version=Oracle GraalVM Enterprise Edition:20.3.3; version=Oracle GraalVM Enterprise Edition:21.2.0

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
5.3Oracle CorporationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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