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Advisory severityLowRed Hat Linux

Low [CVE-2026-54786] Leak in WASIp1 `fd_renumber` implementation

This low-severity Red Hat Linux advisory covers CVE-2026-54786 affecting Red Hat Connectivity Link 1, Red Hat Enterprise Linux 10, Red Hat package: virt-firmware-rs.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-54786 Source published Source updated

VulniPulse record published Record updated

CVE-2026-54786
Affected products & platforms
Red Hat LinuxRed Hat Enterprise Linux
Open source advisory

Summary

Wasmtime is a runtime for WebAssembly. All versions prior to 24.0.10; versions 25.0.0 through those before 36.0.11; versions 37.0.0 through those before 44.0.3; and versions 45.0.0 and 45.0.1 contain a native implementation of WASIp1 which suffers from a leak in the fd_renumber function where the file descriptor being renumbered to is not properly closed.

Wasmtime's implementation erroneously only updated the table of descriptors for WASIp1 and didn't update the underlying table of descriptors used by the host. This behavior means that while fd_renumber works correctly from a guest's perspective it ends up leaking resources in the host that aren't cleaned up until the corresponding Store is destroyed.

In a loop, guests can use fd_renumber to cause hosts to exhaust both resources and file descriptors. This bug only affects the native implementation of WASIp1, meaning that only runtimes which load core wasm modules and expose fd_renumber are affected.

Runtimes are additionally only affected if they expose the ability to acquire a file descriptor, such as opening a file. For runtimes that deny access to files they are unaffected.

This issue has been fixed in versions 24.0.10, 36.0.11, 44.0.3, and 45.0.2. Its native implementation of WASIp1, a system interface for WebAssembly, contains a resource leak in the fd_renumber function.

Is CVE-2026-54786 exploited?

No exploitation is reported in the sources VulniPulse tracks: CVE-2026-54786 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.

How do I fix CVE-2026-54786?

Upgrade to a fixed release named by Red Hat:

  • 24.0.10
  • 36.0.11
  • 44.0.3
  • 45.0.2

Confirm against the vendor advisory before you patch.

Affected versions
  • < 24.0.10
  • < 25.0.0
  • < 36.0.11
  • < 37.0.0
  • < 44.0.3
  • < 45.0.0
  • < 45.0.1

Official advisory · high-confidence parse· fetched 13 days ago·verify at source

Fixed versions
  • 24.0.10
  • 36.0.11
  • 44.0.3
  • 45.0.2

Official advisory · high-confidence parse· fetched 13 days ago·verify at source

Mitigation checklist

Recommended fix / mitigation
  • To mitigate this issue, configure Wasmtime environments to deny guest programs the ability to acquire file descriptors, such as preventing file system access. This restriction limits the attack surface by preventing the `fd_renumber` function from leaking host resources. Consult product-specific documentation for instructions on configuring Wasmtime security policies to restrict file access. If the Wasmtime service is reloaded or restarted, ensure the configuration changes persist.

Official advisory · high-confidence parse· fetched 13 days ago·verify at source

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