CVE-2026-58494

Host file overwrite via mismatched preopen permissions

Published Jul 8, 2026 · Updated Jul 8, 2026

Authorization bypass in Bytecode Alliance Wasmtime allows guest OS users to overwrite read-only host files through WASI filesystem calls. Dir::link_at and Dir::rename_at check directory mutation rights but fail to require equal FilePerms for source and destination preopens. Exploitation requires an embedding with a mutable read-only preopen and a second writable preopen; the Wasmtime CLI is unaffected.

CVSS severity6.5
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in Bytecode Alliance Wasmtime allows guest OS users to overwrite read-only host files through WASI filesystem calls. Dir::link_at and Dir::rename_at check directory mutation rights but fail to require equal FilePerms for source and destination preopens. Exploitation requires an embedding with a mutable read-only preopen and a second writable preopen; the Wasmtime CLI is unaffected.

The record

CVE
CVE-2026-58494
Published
Jul 8, 2026
Updated
Jul 8, 2026
Vendor
Bytecode Alliance
Product
Wasmtime
Classifications
CWE-281, CWE-863, T1565.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 24.0.11
  2. Affected versionversion=>= 25.0.0, < 36.0.12
  3. Affected versionversion=>= 37.0.0, < 45.0.3
  4. Affected versionversion=>= 46.0.0, < 46.0.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Bytecode Alliance · Wasmtimeversion=< 24.0.11; version=>= 25.0.0, < 36.0.12; version=>= 37.0.0, < 45.0.3; version=>= 46.0.0, < 46.0.1

Published CVSS scores

6.5GitHub, Inc.CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-281Improper Preservation of Permissions
CWE-863Incorrect Authorization
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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