CVE-2026-35186Network attack vector

Host crash via mistyped table.grow result

Published Apr 9, 2026 · Updated Apr 9, 2026

Type confusion in affected Wasmtime releases allows remote authenticated users to crash Winch-based hosts via crafted WebAssembly. Winch tags a 32-bit table.grow result as 64-bit, so a failed growth result of -1 becomes an address that reads or writes up to 16 bytes before linear memory. With Winch and default guard pages, the invalid access aborts the host; disabling pre-memory guard pages permits reading or writing up to 16 bytes of host data.

CVSS severity6.1
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Type confusion in affected Wasmtime releases allows remote authenticated users to crash Winch-based hosts via crafted WebAssembly. Winch tags a 32-bit table.grow result as 64-bit, so a failed growth result of -1 becomes an address that reads or writes up to 16 bytes before linear memory. With Winch and default guard pages, the invalid access aborts the host; disabling pre-memory guard pages permits reading or writing up to 16 bytes of host data.

The record

CVE
CVE-2026-35186
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
Bytecode Alliance
Product
Wasmtime
Classifications
CWE-789, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=>= 25.0.0, < 36.0.7
  2. Affected versionversion=>= 37.0.0, < 42.0.2
  3. Affected versionversion=>= 43.0.0, < 44.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Bytecode Alliance · Wasmtimeversion=>= 25.0.0, < 36.0.7; version=>= 37.0.0, < 42.0.2; version=>= 43.0.0, < 44.0.1

Published CVSS scores

6.1GitHub, Inc.CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N
7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-789Memory Allocation with Excessive Size Value
T1499.004Application or System Exploitation

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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