CVE-2026-59644Network attack vector

Member-triggered resource exhaustion via unbounded hash-ratchet iteration

Published Aug 3, 2026 · Updated Aug 3, 2026

Denial of service in Bouncy Castle for Java 1.73 through 1.84 allows remote authenticated users to exhaust CPU and memory. GroupKeySet.HashRatchet.get advances one HKDF step per sender-controlled generation and stores every intermediate KeyGeneration in an unbounded HashMap. Any MLS group member can submit generation 0x7FFFFFFF before per-message signature verification, forcing peers through roughly two billion derivations and multi-gigabyte cache growth.

CVSS severity8.7
High
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Bouncy Castle for Java 1.73 through 1.84 allows remote authenticated users to exhaust CPU and memory. GroupKeySet.HashRatchet.get advances one HKDF step per sender-controlled generation and stores every intermediate KeyGeneration in an unbounded HashMap. Any MLS group member can submit generation 0x7FFFFFFF before per-message signature verification, forcing peers through roughly two billion derivations and multi-gigabyte cache growth.

The record

CVE
CVE-2026-59644
Published
Aug 3, 2026
Updated
Aug 3, 2026
Vendor
Legion of the Bouncy Castle Inc.
Product
Bouncy Castle Java
Classifications
CWE-834, T1499
Attack vector
network
Privileges
authenticated

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=1.73 <1.85

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Legion of the Bouncy Castle Inc. · Bouncy Castle Javaversion=1.73 <1.85

Published CVSS scores

8.7bcorgCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-834Excessive Iteration
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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