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CVE-2023-26314 Mono Project CVE debrief

CVE-2023-26314 is a HIGH severity vulnerability (CVSS 3.1: 8.8) affecting the Mono package in Debian distributions prior to version 6.8.0.105+dfsg-3.3. The vulnerability stems from the association of the application/x-ms-dos-executable MIME type with an unsandboxed Mono CLR interpreter, enabling arbitrary code execution when a user opens a malicious .NET executable file. The attack vector is network-based with low attack complexity, requiring user interaction but no privileges. Affected platforms include Debian Linux 10.0 and specific Mono versions 5.18.0.240+dfsg-3 and 6.8.0.105+dfsg-3. The vulnerability was initially disclosed in January 2023 and formally published in the CVE database on February 22, 2023, with subsequent modifications tracked through May 2026. Debian addressed this through security updates in February 2023.

Vendor
Mono Project
Product
Mono
CVSS
HIGH 8.8
CISA KEV
Not listed in stored evidence
Original CVE published
2023-02-22
Original CVE updated
2026-05-20
Advisory published
2023-02-22
Advisory updated
2026-05-20

Who should care

System administrators managing Debian-based desktop environments, security teams responsible for Linux workstation security, developers using Mono for cross-platform .NET application deployment, and organizations with bring-your-own-device policies allowing Linux systems should prioritize this vulnerability. The risk is particularly elevated for environments where users routinely handle files from untrusted sources, such as email attachments or web downloads.

Technical summary

The vulnerability exists because Debian's Mono package registers the Mono CLR interpreter as the default handler for application/x-ms-dos-executable files without implementing sandboxing restrictions. When a user opens a malicious .NET executable (typically with .exe extension) through a file manager or email client, the Mono runtime executes the code with the user's privileges. The lack of sandboxing allows the executable to perform arbitrary operations including file system access, network connections, and process execution. This represents a significant risk for desktop Linux users who may inadvertently execute malicious Windows-compatible .NET applications. The CVSS score of 8.8 reflects the high impact potential combined with the relatively low barrier to exploitation through social engineering or drive-by download scenarios.

Defensive priority

HIGH

Recommended defensive actions

  • Update Mono package to version 6.8.0.105+dfsg-3.3 or later on all Debian systems
  • Review and restrict file associations for application/x-ms-dos-executable MIME type in desktop environments
  • Implement application sandboxing or containerization for Mono runtime execution where possible
  • Deploy endpoint protection controls to detect and block suspicious .NET executable file execution
  • Audit systems for outdated Mono installations, particularly on Debian 10.0 (Buster) systems
  • Consider disabling automatic execution of downloaded executable files in email clients and web browsers
  • Monitor security advisories from Debian LTS for ongoing vulnerability management

Evidence notes

The vulnerability description is sourced from the official CVE record and NVD entry. Affected product versions are confirmed through CPE criteria in the NVD data. The CVSS vector AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H indicates network attack vector, low complexity, no privileges required, user interaction required, with high impact on confidentiality, integrity, and availability.

Official resources

The vulnerability was publicly disclosed via the oss-security mailing list in January 2023, with official CVE publication following on February 22, 2023. Debian issued a security advisory in February 2023.