# CVE-2026-54786: Wasmtime: Leak in WASIp1 `fd_renumber` implementation > A malicious WebAssembly guest can exhaust host file descriptors via fd_renumber, causing denial of service in Wasmtime runtimes exposing file access. - **Severity:** Low 2.3 (`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`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 1 Jul 2026 - **Updated:** 2 Jul 2026 - **Also known as:** DEBIAN-CVE-2026-54786, GHSA-3p27-qvp9-27qf, JLSEC-2026-1367, MINI-cx8g-cc87-9wcv, MINI-q5m8-f2cv-pr3j, MINI-w46j-9jc9-7p3m, RUSTSEC-2026-0182, UBUNTU-CVE-2026-54786 ## What is CVE-2026-54786? CVE-2026-54786 is a low-severity denial of service vulnerability in bytecodealliance wasmtime, published on 1 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim. ### Official 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. Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime), CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2026-54786? 9 open source packages ship an affected version, including wasmtime-wasi. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `wasmtime-wasi` | crates.io | All versions | 24.0.10 | | `wasmtime-wasi` | crates.io | All versions | 24.0.10 | | `wasmtime-wasi` | crates.io | From 0.0.0-0 | 24.0.10, 36.0.11, 44.0.3, 45.0.2 | | `wasmtime-wasi` | crates.io | From 25.0.0 | 36.0.11 | | `wasmtime-wasi` | crates.io | From 25.0.0 | 36.0.11 | | `wasmtime-wasi` | crates.io | From 37.0.0 | 44.0.3 | | `wasmtime-wasi` | crates.io | From 37.0.0 | 44.0.3 | | `wasmtime-wasi` | crates.io | From 45.0.0 | 45.0.2 | | `wasmtime-wasi` | crates.io | From 45.0.0 | 45.0.2 | Products: Bytecodealliance Wasmtime. ## How do I fix CVE-2026-54786? Upgrade wasmtime-wasi to a fixed version for your release line: 24.0.10, 36.0.11, 44.0.3 or 45.0.2. ## Is CVE-2026-54786 being exploited? There is no known exploitation of CVE-2026-54786 in the wild and no public exploit code. ## Other vulnerabilities in bytecodealliance wasmtime - [CVE-2026-34971](https://insights.sbomify.com/CVE-2026-34971/): Wasmtime miscompiled guest heap access enables sandbox escape on aarch64 Cranelift (critical 9.0) - [CVE-2026-34987](https://insights.sbomify.com/CVE-2026-34987/): Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access (critical 9.0) - [CVE-2022-39393](https://insights.sbomify.com/CVE-2022-39393/): Wasmtime vulnerable to data leakage between instances in the pooling allocator (high 8.6) - [CVE-2022-24791](https://insights.sbomify.com/CVE-2022-24791/): Use after free in Wasmtime (high 8.1) - [CVE-2026-47261](https://insights.sbomify.com/CVE-2026-47261/): Wasmtime: WASI path_open(TRUNCATE) bypasses `FilePerms::WRITE` host restriction (high 7.5) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-54786 and fix it if it is affected. What it is: CVE-2026-54786 is a low-severity denial of service vulnerability in bytecodealliance wasmtime, published on 1 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-54786 in the wild and no public exploit code. Affected packages and fixed versions: - wasmtime-wasi (crates.io): affected all versions; fixed in 24.0.10 - wasmtime-wasi (crates.io): affected all versions; fixed in 24.0.10 - wasmtime-wasi (crates.io): affected from 0.0.0-0; fixed in 24.0.10, 36.0.11, 44.0.3, 45.0.2 - wasmtime-wasi (crates.io): affected from 25.0.0; fixed in 36.0.11 - wasmtime-wasi (crates.io): affected from 25.0.0; fixed in 36.0.11 - wasmtime-wasi (crates.io): affected from 37.0.0; fixed in 44.0.3 - wasmtime-wasi (crates.io): affected from 37.0.0; fixed in 44.0.3 - wasmtime-wasi (crates.io): affected from 45.0.0; fixed in 45.0.2 - wasmtime-wasi (crates.io): affected from 45.0.0; fixed in 45.0.2 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-54786/ (Markdown: https://insights.sbomify.com/CVE-2026-54786/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54786 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54786 - OSV: https://osv.dev/vulnerability/CVE-2026-54786 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-54786/ Summaries are generated and may contain mistakes; the official description above is the record.