CVE-2026-63570 Pkcs12Store.GetCertificateChain loops forever on cyclic issuer links
Attackers can cause denial of service in applications using bc-csharp by supplying crafted PKCS#12 files with cyclic certificate issuer links.
- 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
- None listed
What is CVE-2026-63570?
CVE-2026-63570 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
Loop with unreachable exit condition in Pkcs12Store.GetCertificateChain in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who can supply a crafted PKCS#12 file to an application that loads it and requests a key entry's certificate chain to cause a denial of service, in which the call never returns and consumes CPU and memory until an OutOfMemoryException, via certificates whose issuer links form a cycle, for example two certificates whose AuthorityKeyIdentifier extensions each identify the other's public key. This happens because the chain-building loop stops only when no issuer is found or a certificate links to itself, and keeps no record of certificates already visited. The key-identifier links are followed without checking signatures.
Weakness: CWE-835
Which versions are affected by CVE-2026-63570?
It affects 1 product.
Products include Bouncycastle Bc-Csharp.
How do I fix CVE-2026-63570?
No fix has been published for CVE-2026-63570 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-63570 being exploited?
There is no known exploitation of CVE-2026-63570 in the wild and no public exploit code.
Other vulnerabilities in Legion of the Bouncy Castle Inc. bc-csharp
- CVE-2026-63569 MTI/A0 DHAgreement does not validate the peer's ephemeral value
- CVE-2026-103600 Unbounded ASN.1 nesting depth causes process-terminating stack overflow
- CVE-2026-103603 Unbounded HSS public key level count allows huge array allocation during signature verification
- CVE-2026-103604 Quadratic-time escaping when converting X.509 distinguished names to strings
- CVE-2026-16000 KCcmBlockCipher (DSTU 7624 CCM) tag not bound to nonce when no associated data is used
Sources
Also known as GHSA-g2c8-ppvq-rq73.