# CVE-2026-63578: Unbounded PBE iteration count when decrypting PKCS#8 private keys

> An attacker can cause denial of service via CPU exhaustion by supplying a PKCS#8 private key with an unbounded PBE iteration count in the Bouncy Castle C# library.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 2 Oct 2026
- **Updated:** 6 Oct 2026
- **Also known as:** GHSA-4583-5v2w-p3vq

## What is CVE-2026-63578?

CVE-2026-63578 is a high-severity denial of service vulnerability in Legion of the Bouncy Castle Inc. bc-csharp, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Allocation of resources without limits in password-based private-key decryption (PbeUtilities.GenerateCipherParameters) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who can supply an encrypted private key, such as a PKCS#8 EncryptedPrivateKeyInfo or "ENCRYPTED PRIVATE KEY" PEM file, to cause a denial of service through CPU exhaustion via an iteration count close to 2^31, because the count is taken from the unauthenticated algorithm parameters without an upper bound and the key derivation runs before the password or the data can be checked. PKCS#5 PBES1 and PBES2 (PBKDF2), the PKCS#12 PBE algorithms and CMS password recipients (CmsPbeKey) are affected. Loading PKCS#12 files with Pkcs12Store is covered by CVE-2026-63572, and a zero or negative count with the PKCS#12 algorithms by CVE-2026-63575.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-63578?

It affects 1 product.


Products: Bouncycastle Bc-Csharp.

## How do I fix CVE-2026-63578?

No fix has been published for CVE-2026-63578 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-63578 being exploited?

There is no known exploitation of CVE-2026-63578 in the wild and no public exploit code.

## Other vulnerabilities in Legion of the Bouncy Castle Inc. bc-csharp

- [CVE-2026-63569](https://insights.sbomify.com/CVE-2026-63569/): MTI/A0 DHAgreement does not validate the peer's ephemeral value (critical 9.1)
- [CVE-2026-103600](https://insights.sbomify.com/CVE-2026-103600/): Unbounded ASN.1 nesting depth causes process-terminating stack overflow (high 8.7)
- [CVE-2026-103603](https://insights.sbomify.com/CVE-2026-103603/): Unbounded HSS public key level count allows huge array allocation during signature verification (high 8.7)
- [CVE-2026-103604](https://insights.sbomify.com/CVE-2026-103604/): Quadratic-time escaping when converting X.509 distinguished names to strings (high 8.7)
- [CVE-2026-16000](https://insights.sbomify.com/CVE-2026-16000/): KCcmBlockCipher (DSTU 7624 CCM) tag not bound to nonce when no associated data is used (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63578 and fix it if it is affected.

What it is: CVE-2026-63578 is a high-severity denial of service vulnerability in Legion of the Bouncy Castle Inc. bc-csharp, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-63578 in the wild and no public exploit code.

Affected product: Legion of the Bouncy Castle Inc. bc-csharp. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-63578/ (Markdown: https://insights.sbomify.com/CVE-2026-63578/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63578
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63578
- OSV: https://osv.dev/vulnerability/CVE-2026-63578

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-63578/
Summaries are generated and may contain mistakes; the official description above is the record.