---
id: CVE-2026-17508
title: >-
  In Bouncy Castle for Java before 1.86, several password-based key derivation
  entry points ran the KDF with cost parameters taken from the untrusted input
  being processed, without bounding them, so a small input could dictate an
  arbitrary…
summary: >-
  In Bouncy Castle for Java before 1.86, several password-based key derivation
  entry points ran the KDF with cost parameters taken from the untrusted input
  being processed, without bounding them, so a small input could dictate an
  arbitrary…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/U:Amber'
cwe:
  - CWE-770
vendor: Legion of the Bouncy Castle Inc.
product: bcpkix
affected:
  - bcpkix < 1.86
  - bcprov < 1.86
  - bcpkix-lts8on >= 2.73.0 < 2.73.13
  - bcprov-lts8on >= 2.73.0 < 2.73.13
  - bcpkix-fips >= 1.0.0 < 1.0.13
  - bcpkix-fips >= 2.0.0 < 2.0.13
  - bcpkix-fips >= 2.1.0 < 2.1.13
published: '2026-10-02'
updated: '2026-10-02'
sourceUpdated: '2026-10-02T08:17:01.490'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-17508'
references:
  - url: >-
      https://github.com/bcgit/bc-java/commit/20ed9e203caec91d25cd386ceb6d364e9b068f67
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: >-
      https://github.com/bcgit/bc-java/commit/442393bf187c914b1e66fbed4fab532a1fe06c6a
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: >-
      https://github.com/bcgit/bc-java/commit/480d878aa6f7dc8b20403064f304bbe0decbbb1a
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: >-
      https://github.com/bcgit/bc-java/commit/766a31026ac24ed3c6cad8662058ba450c338da1
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: >-
      https://github.com/bcgit/bc-java/commit/882fdab53f6c4c150a5d6a4e6ef1fc05d382385a
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: >-
      https://github.com/bcgit/bc-java/commit/e72bc0681ff4227fced912ef7394daf7b7d57bb3
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: 'https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9017508'
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
tags:
  - nvd
  - cve.org
cvssSource: cna
ingestedAt: '2026-10-02T08:14:06.224Z'
---

## Overview

In Bouncy Castle for Java before 1.86, several password-based key derivation entry points ran the KDF with cost parameters taken from the untrusted input being processed, without bounding them, so a small input could dictate an arbitrary amount of work before any password or integrity check could reject it. The affected paths are the RFC 9579 PBMAC1 MAC calculator builders, which took the PBKDF2 iteration count and derived-key length straight out of PBMAC1Params (JcePBMac1CalculatorBuilder, and PKCS12PBEUtils.createPBMac1Calculator reached from PKCS12PfxPdu.isMacValid); the scrypt parallelization parameter p in the PKCS#8 and PKCS#12 cost guards, which bounded only the cost parameter N and the block size r even though the scratch buffer scales with r times p, so the configured memory ceiling could be evaded entirely; the raw JCA PBKDF2 provider (org.bouncycastle.jcajce.provider.symmetric.PBEPBKDF2); and the bcrypt round count read from an encrypted OpenSSH v1 private key's own kdfoptions. Each now bounds the parameter before deriving, in line with the caps already applied elsewhere in the tree, with the OpenSSH round count configurable through the new org.bouncycastle.openssh.max_rounds property. This completes the bounding begun in 1.85 for the PKCS#8 / PBES2 decryptors (CVE-2026-15055). This issue also affects Bouncy Castle for Java LTS before 2.73.13, and Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.