---
title: "CVE-2026-17507: Bouncy Castle - Denial of Service"
description: "Bouncy Castle for Java < 1.86 contains a denial of service caused by signed integer misinterpretation of uint32 leaf_index in MLS implementation, letting attackers send crafted messages to exhaust JVM heap, exploit requires membership in group."
url: https://panop.io/threat-heartbeat/CVE-2026-17507/
---

# CVE-2026-17507 Bouncy Castle - Denial of Service

Bouncy Castle for Java < 1.86 contains a denial of service caused by signed integer misinterpretation of uint32 leaf\_index in MLS implementation, letting attackers send crafted messages to exhaust JVM heap, exploit requires membership in group.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.32% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-17507)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Published

2 October 2026

Updated

15 October 2026

Weakness

[CWE-195](https://cwe.mitre.org/data/definitions/195.html)

## Vendor fix

Update to version 1.86 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-17507](https://nvd.nist.gov/vuln/detail/CVE-2026-17507)
- [https://github.com/bcgit/bc-java/commit/1eb83471eb01727bfdb944a5a46355cc77d55f44](https://github.com/bcgit/bc-java/commit/1eb83471eb01727bfdb944a5a46355cc77d55f44)
- [https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9017507](https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9017507)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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