Is CVE-2026-103604 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-103604 being exploited in the wild.

How severe is CVE-2026-103604?

Informational severity, published 2 October 2026.

Which products and versions are affected?

Legion of the Bouncy Castle Inc. Bc-Csharp before 2.7.0.

Is there a fix for CVE-2026-103604?

Yes: fixed in 2.7.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-103604 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-103604?

Check whether you run Legion of the Bouncy Castle Inc. Bc-Csharp at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-103604: Bouncy Castle inefficient X.509 distinguished name parsing

CVE-2026-103604 · Severity: info · Published 2026-10-02

Bouncy Castle is a cryptography library that applications use to parse and validate X.509 certificates and related structures. A flaw in how the library converts certificate distinguished names to strings causes it to work quadratically slower with escaped characters, allowing an attacker to send a specially crafted certificate that exhausts server CPU resources during validation or logging.

Technologies: Legion of the Bouncy Castle Inc. Bc-Csharp. Vendors: Legion of the Bouncy Castle Inc..

Quick answers

Is CVE-2026-103604 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-103604 being exploited in the wild.
How severe is CVE-2026-103604?: Informational severity, published 2 October 2026.
Which products and versions are affected?: Legion of the Bouncy Castle Inc. Bc-Csharp before 2.7.0.
Is there a fix for CVE-2026-103604?: Yes: fixed in 2.7.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-103604 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-103604?: Check whether you run Legion of the Bouncy Castle Inc. Bc-Csharp at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: 2.7.0

Technical details

The vulnerability is an algorithmic complexity flaw in X509Name.ToString and IetfUtilities.ValueToString methods. When processing distinguished name attributes containing escaped characters (commas, spaces) or long values, the code repeatedly rescans buffers with newly inserted backslashes, causing quadratic time complexity. Attacks occur when applications convert names to strings (for logging, display, or comparison) or during PKIX path validation when checking directoryName constraints; no authentication or special privileges are required.

Affected products

Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0

Timeline

2026-10-02: disclosed
2026-06-25: patched

References

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