Cyber Resilience

CVE-2026-34945

Bytecodealliance Wasmtime 25.0.0 – 36.0.7

Published
09 April 2026
Modified
20 April 2026
Patch / advisory
View advisory
CVSS Score v4 2.3
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N/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 0.0032 25th percentile
Risk Priority 27 floored blend · peak EPSS

Summary

CVE-2026-34945 is a low-severity Incorrect Conversion between Numeric Types (CWE-681) vulnerability in Bytecodealliance Wasmtime. Its CVSS base score is 2.3 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 25th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's Winch compiler contains a bug where a 64-bit table, part of the memory64 proposal of WebAssembly, incorrectly translated the table.size instruction. This bug could lead…

more

to disclosing data on the host's stack to WebAssembly guests. The host's stack can possibly contain sensitive data related to other host-originating operations which is not intended to be disclosed to guests. This bug specifically arose from a mistake where the return value of table.size was statically typed as a 32-bit integer, as opposed to consulting the table's index type to see how large the returned register could be. When combined with details about Wnich's ABI, such as multi-value returns, this can be combined to read stack data from the host, within a guest. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.

CWE(s)
CWE-681

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 →
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-2024-30266Same product: Bytecodealliance Wasmtime
CVE-2023-41880Same product: Bytecodealliance Wasmtime
CVE-2026-34983Same product: Bytecodealliance Wasmtime
CVE-2026-24116Same product: Bytecodealliance Wasmtime
CVE-2026-34941Same product: Bytecodealliance Wasmtime
CVE-2026-34942Same product: Bytecodealliance Wasmtime
CVE-2026-34988Same product: Bytecodealliance Wasmtime
CVE-2023-30624Same product: Bytecodealliance Wasmtime
CVE-2025-53901Same product: Bytecodealliance Wasmtime
CVE-2026-34987Same product: Bytecodealliance Wasmtime

Affected Assets

bytecodealliance
wasmtime
25.0.0 — 36.0.7 · 37.0.0 — 42.0.2 · 43.0.0 — 43.0.1

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover incorrect numeric conversions through targeted test cases.

SA-8 Security and Privacy Engineering Principles partial match

Engineering principles can mandate safe numeric handling and range checks that structurally avoid bad conversions.

SI-10 Information Input Validation partial match

Input validation directly stops malformed or out-of-range numeric values from reaching conversion logic.

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 code reviews, static analysis, and developer training that catch and prevent numeric type-conversion errors.

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 can detect numeric conversion defects before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle includes type-safety and conversion checks that reduce numeric truncation risks.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate safe numeric handling and range validation.

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

Secure architecture principles promote strong typing and safe conversion practices.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly address correct numeric type conversions and overflow checks.

References