CVE-2021-35556Network attack vector

Client denial of service via oversized RTF binary

Published Oct 20, 2021 · Updated May 28, 2026

Resource exhaustion in Swing RTF parsing in Oracle Java SE 7u311, 8u301, 11.0.12, and 17 allows remote attackers to interrupt clients. RTFParser trusts an untrusted \bin length and preallocates a ByteArrayOutputStream as large as Integer.MAX_VALUE, exhausting heap memory. Reachability requires a sandboxed Java Web Start application or applet to load untrusted RTF content; trusted-code-only server deployments are not affected.

CVSS severity5.3
Medium
EPSS probability8.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Swing RTF parsing in Oracle Java SE 7u311, 8u301, 11.0.12, and 17 allows remote attackers to interrupt clients. RTFParser trusts an untrusted \bin length and preallocates a ByteArrayOutputStream as large as Integer.MAX_VALUE, exhausting heap memory. Reachability requires a sandboxed Java Web Start application or applet to load untrusted RTF content; trusted-code-only server deployments are not affected.

The record

CVE
CVE-2021-35556
Published
Oct 20, 2021
Updated
May 28, 2026
Vendor
Oracle Corporation
Product
Java Platform, Standard Edition (Java SE)
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 20, 2021CVE publishedPublication date reported by the CVE source.
  2. May 28, 2026Record 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
5.3OracleCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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