---
title: "CVE-2026-18036: Bouncy Castle - Timing Side-Channel Information Disclosure"
description: "Bouncy Castle for Java < 1.86 contains a timing side-channel vulnerability caused by secret-dependent integer division in NTRU polynomial reduction, letting attackers recover private key information via timing analysis, exploit requires precise timing measurement."
url: https://panop.io/threat-heartbeat/CVE-2026-18036/
---

# CVE-2026-18036 Bouncy Castle - Timing Side-Channel Information Disclosure

Bouncy Castle for Java < 1.86 contains a timing side-channel vulnerability caused by secret-dependent integer division in NTRU polynomial reduction, letting attackers recover private key information via timing analysis, exploit requires precise timing measurement.

CVSS base score 8.2 /10

High

CISA KEV

Not listed

Public exploit

None known

EPSS

0.28% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-18036)

## Details

Type

Timing Side-Channel Information Disclosure

Impact

Information Disclosure

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber

Published

2 October 2026

Updated

15 October 2026

Weakness

[CWE-208](https://cwe.mitre.org/data/definitions/208.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-2026-18036](https://nvd.nist.gov/vuln/detail/CVE-2026-18036)
- [https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4](https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4)
- [https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9018036](https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9018036)

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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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