CVE-2026-54786
Wasmtime: Leak in WASIp1 `fd_renumber` implementation
Description
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.
INFO
Published Date :
July 1, 2026, 9:17 p.m.
Last Modified :
July 2, 2026, 7:27 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | LOW | [email protected] |
Solution
- Update Wasmtime to version 24.0.10 or later.
- Update Wasmtime to version 36.0.11 or later.
- Update Wasmtime to version 44.0.3 or later.
- Update Wasmtime to version 45.0.2 or later.
Public PoC/Exploit Available at Github
CVE-2026-54786 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-54786.
| URL | Resource |
|---|---|
| https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3p27-qvp9-27qf | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-54786 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-54786
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Swift 6 Wasmtime wrapper for SwiftPM, vendoring the official C API artifacts for most Apple platforms, Linux, and Windows.
c-api linux macos swift swift-package-manager swift6 wasi wasm wasmtime webassembly windows ios ipados tvos
Swift C C++ Shell
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-54786 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-54786 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jul. 02, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L Added CPE Configuration OR *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions up to (excluding) 24.0.10 *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions from (including) 25.0.0 up to (excluding) 36.0.11 *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions from (including) 37.0.0 up to (excluding) 44.0.3 *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions from (including) 45.0.0 up to (excluding) 45.0.2 Added Reference Type GitHub, Inc.: https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3p27-qvp9-27qf Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 02, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-54786', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-02T12:44:47.360688Z'} -
New CVE Received by [email protected]
Jul. 01, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'bytecodealliance', 'product': 'wasmtime', 'versions': [{'status': 'affected', 'version': '< 24.0.10'}, {'status': 'affected', 'version': '>= 25.0.0, < 36.0.11'}, {'status': 'affected', 'version': '>= 37.0.0, < 44.0.3'}, {'status': 'affected', 'version': '>= 45.0.0, < 45.0.2'}]}] Added Description 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. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-400 Added CWE CWE-772 Added Reference https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3p27-qvp9-27qf