CVE-2026-59650Network attack vector

Static DH key recovery via unchecked peer element

Published Aug 3, 2026 · Updated Aug 3, 2026

Improper input validation in Bouncy Castle Java before 1.85 and LTS before 2.73.12 allows remote attackers to recover static DH keys. DHAgreement.calculateAgreement exponentiates the raw peer-supplied message with the local static private key without range or subgroup checks. Remote attackers must act as MTI/A0 peers and repeat small-order exchanges to derive the reused key, enabling decryption or forgery.

CVSS severity9.3
Critical
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Bouncy Castle Java before 1.85 and LTS before 2.73.12 allows remote attackers to recover static DH keys. DHAgreement.calculateAgreement exponentiates the raw peer-supplied message with the local static private key without range or subgroup checks. Remote attackers must act as MTI/A0 peers and repeat small-order exchanges to derive the reused key, enabling decryption or forgery.

The record

CVE
CVE-2026-59650
Published
Aug 3, 2026
Updated
Aug 3, 2026
Vendor
Legion of the Bouncy Castle Inc.
Product
Bouncy Castle Java
Classifications
CWE-20
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 Java LTSversion=2.73.0 <2.73.12

Published CVSS scores

9.3Legion of the Bouncy Castle Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA: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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation

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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