VulnerabilityPublished 12 Nov 2025

CVE-2025-64345: bytecodealliance wasmtime · Race Condition

Affects bytecodealliance wasmtimeSource CVE Database V5

Not known to be exploited · CVSS 1.8 Low : upgrade to 24.0.5 when convenient.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

1.8Low

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 24.0.5

CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:U/C:N/I:L/A:N

Attack Vector: Local
Attack Complexity: High
Privileges Required: High
User Interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Nov 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade bytecodealliance/wasmtime to 24.0.5.

Affected software

Product	Affected	Fixed in
crates.iobytecodealliance/wasmtime`pkg:cargo/bytecodealliance/wasmtime`Other threats	Affected <24.0.5	Fixed in 24.0.5

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Wasmtime to the latest patched versions: 24.0.5, 36.0.3, 37.0.3, or 38.0.4 or later.
Modify embedding code to use SharedMemory::new instead of Memory::new when creating shared linear memories to ensure proper synchronization and soundness.
Disable core dumps in environments where upgrading or code changes are not immediately possible to prevent inconsistent memory state exposure.
Conduct code audits of Wasmtime embedding implementations to verify correct usage of shared memory APIs and absence of unsafe concurrency patterns.
Implement strict access controls to limit local high-privilege user access to hosts running Wasmtime to reduce exploitation risk.
Monitor Wasmtime runtime logs and application behavior for anomalies indicative of data races or memory corruption.
Educate development teams on safe concurrency practices when working with WebAssembly shared memory and Rust embedding APIs.
Consider sandboxing or isolating Wasmtime processes to contain potential integrity issues.
Stay informed on Wasmtime security advisories for any future updates or related vulnerabilities.

Description

Wasmtime is a runtime for WebAssembly. Prior to version 38.0.4, 37.0.3, 36.0.3, and 24.0.5, Wasmtime's Rust embedder API contains an unsound interaction where a WebAssembly shared linear memory could be viewed as a type which provides safe access to the host (Rust) to the contents of the linear memory. This is not sound for shared linear memories, which could be modified in parallel, and this could lead to a data race in the host. Patch releases have been issued for all supported versions of Wasmtime, notably: 24.0.5, 36.0.3, 37.0.3, and 38.0.4. These releases reject creation of shared memories via `Memory::new` and shared memories are now excluded from core dumps. As a workaround, eembeddings affected by this issue should use `SharedMemory::new` instead of `Memory::new` to create shared memories. Affected embeddings should also disable core dumps if they are unable to upgrade. Note that core dumps are disabled by default but the wasm threads proposal (and shared memory) is enabled by default.

Impact

For European organizations, the primary impact of CVE-2025-64345 lies in potential data integrity issues within applications embedding Wasmtime, especially those leveraging shared linear memory for concurrent WebAssembly threads. While the vulnerability does not directly compromise confidentiality or availability, data races can lead to unpredictable application behavior, subtle corruption of in-memory data structures, and potential downstream logic errors. This can affect software development tools, cloud-native applications, or edge computing platforms that integrate Wasmtime for WebAssembly execution. Organizations relying on Wasmtime in critical infrastructure or security-sensitive environments may face increased risk of integrity violations, complicating debugging and potentially undermining trust in application correctness. The requirement for local high-privilege access and user interaction limits the threat surface primarily to insider threats or compromised hosts. However, given the growing adoption of WebAssembly runtimes in European tech sectors, unpatched deployments could inadvertently introduce stability and integrity risks. The exclusion of shared memories from core dumps mitigates some risk of sensitive data leakage during crash analysis. Overall, the impact is low but non-negligible for organizations embedding Wasmtime in complex concurrent environments.

Summary

CVE-2025-64345 is a concurrency vulnerability classified under CWE-362 (Race Condition) found in the Wasmtime WebAssembly runtime developed by bytecodealliance. Wasmtime allows embedding WebAssembly modules in host applications, with shared linear memory enabling concurrent threads to access the same memory region. Prior to versions 24.0.5, 36.0.3, 37.0.3, and 38.0.4, the Rust embedder API incorrectly allowed shared linear memory to be accessed via a type that assumes safe, exclusive access. This unsound assumption leads to potential data races when multiple threads modify the shared memory concurrently, causing undefined behavior and possible data corruption in the host environment. The vulnerability does not expose confidentiality breaches or availability disruptions but can compromise data integrity within the host process. Exploitation requires local access with high privileges and user interaction, making remote exploitation unlikely. The Wasmtime team patched this issue by rejecting shared memory creation through the unsafe Memory::new API and recommending the use of SharedMemory::new, which enforces proper synchronization. Additionally, shared memories are excluded from core dumps to prevent leakage of inconsistent memory states. Organizations embedding Wasmtime should upgrade to the fixed versions or apply the recommended API usage changes. If upgrading is not feasible, disabling core dumps is advised to reduce risk. No known exploits are reported in the wild, and the CVSS v3.1 score is low (1.8) due to the limited impact and exploitation complexity.

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Architecture and Design
In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
Architecture and Design
Use thread-safe capabilities such as the data access abstraction in Spring.
Architecture and Design
Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.2 (opens in a new tab)
Attack patterns
Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Nov 2025, 21:39 UTC

WeaknessesCWE-362

Technical details

References

Community reviews

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