CVE-2026-59642Network attack vector

Undetected authenticated content substitution via unchecked messageDigest

Published Aug 3, 2026 · Updated Aug 3, 2026

Improper integrity validation in affected Bouncy Castle Java CMS libraries allows remote attackers to alter authenticated content undetected. RecipientInformation.getContentStream() digests content without a key, while getMac() authenticates only DER-encoded authAttrs and never compares that digest with the messageDigest attribute. Exploitation requires an application to process attacker-controlled CMS AuthenticatedData with authAttrs; modified eContent then passes the documented MAC comparison.

CVSS severity8.7
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper integrity validation in affected Bouncy Castle Java CMS libraries allows remote attackers to alter authenticated content undetected. RecipientInformation.getContentStream() digests content without a key, while getMac() authenticates only DER-encoded authAttrs and never compares that digest with the messageDigest attribute. Exploitation requires an application to process attacker-controlled CMS AuthenticatedData with authAttrs; modified eContent then passes the documented MAC comparison.

The record

CVE
CVE-2026-59642
Published
Aug 3, 2026
Updated
Aug 3, 2026
Vendor
Legion of the Bouncy Castle Inc.
Product
Bouncy Castle Java
Classifications
CWE-354, T1565.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=0 <1.85

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Legion of the Bouncy Castle Inc. · Bouncy Castle Javaversion=0 <1.85
Legion of the Bouncy Castle Inc. · Bouncy Castle FIPS Java APIversion=1.0.0 <1.0.12; version=2.0.0 <2.0.12; version=2.1.0 <2.1.12
Legion of the Bouncy Castle Inc. · Bouncy Castle Java LTSversion=2.73.0 <2.73.12

Published CVSS scores

8.7Bouncy Castle CNACVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
7.5Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

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

CWE-354Improper Validation of Integrity Check Value
T1565.002Transmitted Data Manipulation

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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