CVE-2025-53901VulnerabilityPublished 18 Jul 2025

CVE-2025-53901: bytecodealliance wasmtime · Operation on a Resource after Expiration or Release

Affects bytecodealliance wasmtimeSource CVE Database V5

Not known to be exploited · CVSS 3.5 Low : upgrade to 24.0.4 when convenient.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

3.5Low

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 31% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 24.0.4

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

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Jul 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 2026-10-26.

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 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 24.0.4.

Affected software

Product	Affected	Fixed in
crates.iobytecodealliance/wasmtime`pkg:cargo/bytecodealliance/wasmtime`Other threats	Affected <24.0.4	Fixed in 24.0.4

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

AI-suggested

The definitive mitigation is to upgrade all Wasmtime deployments to the patched versions 24.0.4, 33.0.2, or 34.0.2 as appropriate. Organizations should audit their use of Wasmtime to identify embeddings that expose WASIp1 interfaces with preopened directories allowing file descriptor creation. Where upgrading is temporarily not feasible, consider restricting guest capabilities to prevent opening new file descriptors or disable the use of `fd_renumber` if possible. Embedders using WASIp2 or component-based embeddings are not affected and should verify their configurations accordingly. Additionally, implement runtime monitoring to detect abnormal panics or crashes in Wasmtime hosts, enabling rapid incident response. Incorporate WebAssembly module validation and sandboxing best practices to limit the ability of untrusted modules to invoke problematic sequences. Finally, maintain up-to-date inventories of Wasmtime versions in use and integrate vulnerability scanning into CI/CD pipelines to ensure timely patch application.

Description

Wasmtime is a runtime for WebAssembly. Prior to versions 24.0.4, 33.0.2, and 34.0.2, a bug in Wasmtime's implementation of the WASIp1 set of import functions can lead to a WebAssembly guest inducing a panic in the host (embedder). The specific bug is triggered by calling `path_open` after calling `fd_renumber` with either two equal argument values or a second argument being equal to a previously-closed file descriptor number value. The corrupt state introduced in `fd_renumber` will lead to the subsequent opening of a file descriptor to panic. This panic cannot introduce memory unsafety or allow WebAssembly to break outside of its sandbox, however. There is no possible heap corruption or memory unsafety from this panic. This bug is in the implementation of Wasmtime's `wasmtime-wasi` crate which provides an implementation of WASIp1. The bug requires a specially crafted call to `fd_renumber` in addition to the ability to open a subsequent file descriptor. Opening a second file descriptor is only possible when a preopened directory was provided to the guest, and this is common amongst embeddings. A panic in the host is considered a denial-of-service vector for WebAssembly embedders and is thus a security issue in Wasmtime. This bug does not affect WASIp2 and embedders using components. In accordance with Wasmtime's release process, patch releases are available as 24.0.4, 33.0.2, and 34.0.2. Users of other release of Wasmtime are recommended to move to a supported release of Wasmtime. Embedders who are using components or are not providing guest access to create more file descriptors (e.g.via a preopened filesystem directory) are not affected by this issue. Otherwise, there is no workaround at this time, and affected embeddings are recommended to update to a patched version which will not cause a panic in the host.

Impact

For European organizations, the primary impact of CVE-2025-53901 is a potential denial-of-service condition in applications or services embedding Wasmtime to run WebAssembly workloads. This could disrupt critical services relying on WebAssembly for sandboxed execution, such as serverless platforms, edge computing nodes, or embedded systems that utilize Wasmtime for extensibility or plugin architectures. While the vulnerability does not compromise data confidentiality or integrity, repeated or targeted exploitation could degrade service availability, leading to operational interruptions and potential financial or reputational damage. Organizations deploying Wasmtime in multi-tenant environments or exposed to untrusted WebAssembly modules are at higher risk. Given the growing adoption of WebAssembly in cloud-native and edge environments across Europe, especially in sectors like finance, telecommunications, and manufacturing, this vulnerability could affect service reliability if unpatched. However, the requirement for specific guest capabilities and the absence of memory corruption limit the scope of impact to denial-of-service scenarios only.

Summary

CVE-2025-53901 is a vulnerability identified in the Wasmtime runtime for WebAssembly, specifically affecting versions prior to 24.0.4, 33.0.2, and 34.0.2. Wasmtime implements WASIp1 import functions through its wasmtime-wasi crate. The vulnerability arises from improper handling of file descriptor operations, specifically when a WebAssembly guest calls the `fd_renumber` function with either two identical arguments or when the second argument matches a previously closed file descriptor number. This misuse corrupts the internal state of Wasmtime's file descriptor management. Subsequently, invoking `path_open` to open a new file descriptor triggers a panic in the host runtime due to this corrupted state. Although this panic causes a denial-of-service (DoS) condition by crashing the host, it does not lead to memory corruption, heap corruption, or sandbox escape, preserving the integrity and confidentiality of the host system. The vulnerability requires the attacker to have the ability to execute a crafted sequence of WASI calls, including `fd_renumber` and `path_open`, which is possible only if the WebAssembly guest has access to preopened directories—a common scenario in many Wasmtime embeddings. Notably, this issue does not affect WASIp2 or embedders using components, nor those that restrict guest capabilities to open new file descriptors. There is no known workaround other than upgrading to patched versions 24.0.4, 33.0.2, or 34.0.2. The CVSS v3.1 base score is 3.5 (low severity), reflecting the limited impact (denial of service only), network attack vector, low attack complexity, requirement for privileges (PR:L), and user interaction (UI:R). No known exploits are reported in the wild as of publication.

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 18 Jul 2025, 17:46 UTC

WeaknessesCWE-672

Technical details

References

Community reviews

Related threats