Wasmtime: WASI hard links bypass wasmtime-wasi's FilePerms for destination

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N

EPSS

• CVE-2026-58494: 0.17% estimated exploitation activity in the next 30 days; percentile 6.51 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Wasmtime's WASI filesystem implementation lets a guest with a read-only source file capability overwrite that file by hard-linking it into another preopen that allows file writes. An attacker who can run a WASI guest can bypass WasiCtxBuilder per-preopen FilePerms and modify host files that were exposed as FilePerms::READ. This attack is possible through the wasip1, wasip2, and wasip3 interfaces to the WASI filesystem. This attack is also possible through an indirection of renaming a hardlink into another preopen. Details WasiCtxBuilder::preopeneddir documents fileperms as the maximum permissions usable for files in that preopen. However, hard-link creation and renaming only checked directory mutation for permission, and not whether the file permissions matched. This makes an attack possible where: a read-only file target exists in a preopen with only FilePerms::READ a hardlink named alias, with destination to the target, is created in a preopen with FilePerms::READ |…

Published by the source

16 Oct 2026, 19:57 UTC

Last modified by the source

16 Oct 2026, 20:15 UTC

Source last checked

26 Oct 2026, 15:43 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4ch3-9j33-3pmj

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-4ch3-9j33-3pmj

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# Patch Next advisory brief: CVE-2026-58494

Advisory: Wasmtime: WASI hard links bypass wasmtime-wasi's FilePerms for destination
IDs: CVE-2026-58494, GHSA-4ch3-9j33-3pmj
Record: https://patchnext.com/advisories/cve-2026-58494 (revision 2, source checked 26 Oct 2026, 15:43 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: wasmtime-wasi 46.0.1, 45.0.3, 36.0.12, 24.0.11. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io wasmtime-wasi: affected < 24.0.11; >= 25.0.0, < 36.0.12; >= 37.0.0, < 45.0.3; >= 46.0.0, < 46.0.1; fixed in 24.0.11, 45.0.3, 46.0.1, 36.0.12

## Suggested inspection (read-only)
- crates.io wasmtime-wasi: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on wasmtime-wasi.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-4ch3-9j33-3pmj (OSV record GHSA-4ch3-9j33-3pmj lists affected ranges: crates.io wasmtime-wasi >=0 =25.0.0 =37.0.0 =46.0.0 <46.0.1 (fixed))
- Verified: https://github.com/advisories/GHSA-4ch3-9j33-3pmj (GitHub-reviewed advisory GHSA-4ch3-9j33-3pmj lists affected ranges: crates.io wasmtime-wasi >=0 =25.0.0 =37.0.0 =46.0.0 <46.0.1)

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