Cyber Resilience

CVE-2026-34942

Bytecodealliance Wasmtime ≤ 24.0.7

Published
09 April 2026
Modified
20 April 2026
Patch / advisory
View advisory
CVSS Score v4 5.9
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0035 28th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-34942 is a medium-severity Improper Validation of Array Index (CWE-129) vulnerability in Bytecodealliance Wasmtime. Its CVSS base score is 5.9 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 28th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

A05:2025 Injection

EU & UK References

Vulnerability Data

Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings into the Component Model's utf16 or latin1+utf16 encodings improperly verified the alignment of reallocated strings. This meant that unaligned pointers could be…

more

passed to the host for transcoding which would trigger a host panic. This panic is possible to trigger from malicious guests which transfer very specific strings across components with specific addresses. Host panics are considered a DoS vector in Wasmtime as the panic conditions are controlled by the guest in this situation. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.

CWE(s)
CWE-129

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-34941Same product: Bytecodealliance Wasmtime
CVE-2026-24116Same product: Bytecodealliance Wasmtime
CVE-2026-34987Same product: Bytecodealliance Wasmtime
CVE-2026-34971Same product: Bytecodealliance Wasmtime
CVE-2026-35195Same product: Bytecodealliance Wasmtime
CVE-2023-41880Same product: Bytecodealliance Wasmtime
CVE-2024-30266Same product: Bytecodealliance Wasmtime
CVE-2026-34983Same product: Bytecodealliance Wasmtime
CVE-2026-34945Same product: Bytecodealliance Wasmtime
CVE-2023-30624Same product: Bytecodealliance Wasmtime

Affected Assets

bytecodealliance
wasmtime
≤ 24.0.7 · 25.0.0 — 36.0.7 · 37.0.0 — 42.0.2

Mitigating Controls

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input validation and bounds checking that prevent improper array indexing.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development can detect out-of-bounds array access but does not prevent the weakness by itself.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and bounds checking that directly prevents improper array indexing.

A.8.26 Application security requirements partial match
prevents

Application security requirements include validation of untrusted input used for indexing or addressing memory structures.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles encourage defensive coding patterns that reduce index-related vulnerabilities.

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly require bounds checking and validation of array indices derived from untrusted data.

References