CVE-2026-63568: Allocation of resources without limits or throttling in the CMP/CRMF password-based MAC verifier (PKMacBuilder

Q: How do I fix CVE-2026-63568?

bc-csharp: upgrade to 2.7.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-63568 being exploited?

CVE-2026-63568 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-63568 affect?

CVE-2026-63568 affects bc-csharp. Severity is high (CVSS 7.5). Allocation of resources without limits or throttling in the CMP/CRMF password-based MAC verifier (PKMacBuilder) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker to cause a denial of service

Q: How urgent is CVE-2026-63568?

Priority 37/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-63568 is a high-severity flaw (CVSS 7.5) affecting bc-csharp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Allocation of resources without limits or throttling in the CMP/CRMF password-based MAC verifier (PKMacBuilder) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker to cause a denial of service through CPU exhaustion via a CMP message or CRMF certificate request whose PBMParameter declares a very large iteration count, because PKMacBuilder enforced its iteration-count ceiling only when the caller had

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 75%)
CISA exploited list	No
Weakness	CWE-770
Published	2026-10-02
Last modified	2026-10-27

Publisher (CNA): bcorg · Vendor: bouncycastle

Last updated 2026-10-27 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-10-02 07:16 UTCPublished CVE record published
2026-10-27 16:05 UTCUpdated Record last modified

bouncycastle bc-csharp UPGRADE

Affected: < 2.7.0

Fixed in: 2.7.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy bc-csharp || rpm -q bc-csharp || bc-csharp --version

2. UPGRADE to 2.7.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bc-csharp

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bc-csharp

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-63568?

bc-csharp: upgrade to 2.7.0. Exact commands for each OS are on this page.

Is CVE-2026-63568 being exploited?

CVE-2026-63568 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-63568 affect?

CVE-2026-63568 affects bc-csharp. Severity is high (CVSS 7.5). Allocation of resources without limits or throttling in the CMP/CRMF password-based MAC verifier (PKMacBuilder) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker to cause a denial of service

How urgent is CVE-2026-63568?

Priority 37/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-63578 HIGH 7.5 UPGRADE Allocation of resources without limits in password-based private-key decryption (PbeUtilities.GenerateCipherPa
CVE-2026-103602 MEDIUM 5.3 UPGRADE Improper certificate validation in PkixNameConstraintValidator in Legion of the Bouncy Castle Inc
CVE-2026-103603 HIGH 7.5 UPGRADE Memory allocation with excessive size value in the HSS/LMS signature code (HssPublicKeyParameters, HssSignatur
CVE-2026-103604 HIGH 7.5 UPGRADE Inefficient algorithmic complexity in X.509 distinguished name string conversion (X509Name.ToString and IetfUt
CVE-2026-63570 HIGH 7.5 UPGRADE Loop with unreachable exit condition in Pkcs12Store.GetCertificateChain in Legion of the Bouncy Castle Inc

References

← Back to latest CVEs