CVE-2026-54786CWE-400CWE-772

Wasmtime: Leak in WASIp1 `fd_renumber` implementation

Low · published July 1, 2026

CVSS v4.0
2.3
EPSS
0%
Percentile
29.4
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
2.3 · LOW
Vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L
EPSS
0.00367 · 29.4th percentile
Weaknesses
CWE-400 · Uncontrolled Resource Consumption; CWE-772 · Missing Release of Resource after Effective Lifetime
Published
2026-07-01T20:12Z
EPSS history
Timeline
  • 01 JUL 20:12Z
    Wasmtime: Leak in WASIp1 `fd_renumber` implementation
    cvelistv5