CVE-2026-47261Network attack vector

Host-file truncation via omitted write-mode check

Published Jun 15, 2026 · Updated Jun 15, 2026

Improper access control in Wasmtime allows attackers to truncate host files through crafted WASI file-open requests. Dir::open_at treats OpenFlags::TRUNCATE as a write for the host operation but omits OpenMode::WRITE from the later FilePerms authorization check. Exposure requires a wasmtime-wasi embedding configured with DirPerms::MUTATE and FilePerms::READ without WRITE; the Wasmtime CLI is not affected.

CVSS severity7.5
High
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Wasmtime allows attackers to truncate host files through crafted WASI file-open requests. Dir::open_at treats OpenFlags::TRUNCATE as a write for the host operation but omits OpenMode::WRITE from the later FilePerms authorization check. Exposure requires a wasmtime-wasi embedding configured with DirPerms::MUTATE and FilePerms::READ without WRITE; the Wasmtime CLI is not affected.

The record

CVE
CVE-2026-47261
Published
Jun 15, 2026
Updated
Jun 15, 2026
Vendor
Bytecode Alliance
Product
Wasmtime
Classifications
CWE-284, T1565.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 15, 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=< 24.0.9
  2. Affected versionversion=>= 25.0.0, < 36.0.10
  3. Affected versionversion=>= 37.0.0, < 44.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Bytecode Alliance · Wasmtimeversion=< 24.0.9; version=>= 25.0.0, < 36.0.10; version=>= 37.0.0, < 44.0.2

Published CVSS scores

7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
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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