CVE-2026-34941Network attack vector

Host crash via undersized transcoder bounds check

Published Apr 9, 2026 · Updated Apr 9, 2026

Out-of-bounds read in affected Wasmtime releases allows attackers to crash the host through crafted UTF-16 component-model input. The UTF-16-to-latin1+utf16 transcoder checks the code-unit count rather than the byte length, allowing a host read twice the validated size beyond guest linear memory. Default guard pages turn the read into a segfault; disabling guard pages can expose adjacent host memory for interpretation as UTF-16.

CVSS severity6.9
Medium
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in affected Wasmtime releases allows attackers to crash the host through crafted UTF-16 component-model input. The UTF-16-to-latin1+utf16 transcoder checks the code-unit count rather than the byte length, allowing a host read twice the validated size beyond guest linear memory. Default guard pages turn the read into a segfault; disabling guard pages can expose adjacent host memory for interpretation as UTF-16.

The record

CVE
CVE-2026-34941
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
Bytecode Alliance
Product
Wasmtime
Classifications
CWE-125, T1499
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

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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=< 24.0.7
  2. Affected versionversion=>= 25.0.0, < 36.0.7
  3. Affected versionversion=>= 37.0.0, < 42.0.2
  4. Affected versionversion=>= 43.0.0, < 44.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Bytecode Alliance · Wasmtimeversion=< 24.0.7; version=>= 25.0.0, < 36.0.7; version=>= 37.0.0, < 42.0.2; version=>= 43.0.0, < 44.0.1

Published CVSS scores

6.9GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/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-125Out-of-bounds Read
T1499Endpoint Denial of Service

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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