# CVE-2026-84008: Inefficient algorithmic complexity in .NET allows an unauthorized attacker to deny service over a network.

Source: https://junglewise.ai/threats/cve-2026-84008-microsoft-security-advisory-net-denial-of-service-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-13  
License: CC BY 4.0 with a link back

CVE-2026-84008 · Severity: high · CVSS 7.5 · Published 2026-10-13

System.Security.Cryptography.Pkcs is a .NET library that handles digital signatures and cryptographic operations in applications. An attacker can send specially crafted certificate data that causes the SignedCms.CheckSignature method to repeatedly reparse the data, consuming CPU resources and potentially crashing or disabling the affected application without authentication.

Technologies: [System.Security.Cryptography.Pkcs (NuGet)](https://junglewise.ai/threats/technologies/system-security-cryptography-pkcs). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft), [NuGet](https://junglewise.ai/threats/vendors/nuget).

## Quick answers

**Is CVE-2026-84008 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-84008 being exploited in the wild.

**How severe is CVE-2026-84008?** High severity, with a CVSS score of 7.5, published 13 October 2026.

**Which products and versions are affected?** Microsoft System.Security.Cryptography.Pkcs 10.0.0 through 10.0.12, 11.0.0-preview.1 through 11.0.0-rc.1, 8.0.0 through 8.0.1, 9.0.0 through 9.0.20; System.Security.Cryptography.Pkcs (NuGet) >= 10.0.0, <= 10.0.12, ECOSYSTEM:introduced=10.0.0,fixed=10.0.13.

**Is there a fix for CVE-2026-84008?** Yes. System.Security.Cryptography.Pkcs (NuGet): upgrade to 10.0.13 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-84008 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-84008?** Check whether you run Microsoft System.Security.Cryptography.Pkcs or System.Security.Cryptography.Pkcs (NuGet) 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

- System.Security.Cryptography.Pkcs (NuGet): upgrade to 10.0.13 or later

  ```sh
  dotnet add package System.Security.Cryptography.Pkcs --version 10.0.13
  ```


## Technical details

The vulnerability is an algorithmic complexity flaw (CWE-407) in the SignedCms.CheckSignature method, which reprocesses attacker-controlled X.509 certificate data quadratically, leading to CPU exhaustion. The attack requires network access and no authentication or user interaction. A remote attacker can exploit this to cause denial of service by exhausting server CPU resources.

## Affected products

- Microsoft System.Security.Cryptography.Pkcs 10.0.0 through 10.0.12, 11.0.0-preview.1 through 11.0.0-rc.1, 8.0.0 through 8.0.1, 9.0.0 through 9.0.20

## Identifiers

- CVE-2026-84008
- GHSA-846f-f764-76mx

## Timeline

- 2026-10-13: disclosed

## Related threats

- [.NET System.Security.Cryptography.Pkcs denial of service](https://junglewise.ai/threats/cve-2026-70162-microsoft-security-advisory-net-denial-of-service-vulnerability)
- [.NET Denial of Service vulnerability](https://junglewise.ai/threats/cve-2023-29331-net-denial-of-service-vulnerability)