# CVE-2026-119143: Wasmtime denial of service in component model stream operations

Source: https://junglewise.ai/threats/cve-2026-119143-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-29. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

CVE-2026-119143 · Severity: medium · CVSS 4.8 · Published 2026-10-29

Wasmtime is a WebAssembly runtime used to execute untrusted guest code in embedded systems and services. A vulnerability in its component model stream handling allows malicious guest code to crash the host system by triggering a panic through zero-length stream operations with out-of-bounds addresses. This denial of service affects any application that uses Wasmtime's WASIp3 implementation or the Direct stream APIs.

Technologies: [Bytecode Alliance Wasmtime](https://junglewise.ai/threats/technologies/bytecode-alliance-wasmtime). Vendors: [Bytecode Alliance](https://junglewise.ai/threats/vendors/bytecode-alliance).

## Quick answers

**Is CVE-2026-119143 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-119143 being exploited in the wild.

**How severe is CVE-2026-119143?** Medium severity, with a CVSS score of 4.8, published 29 October 2026.

**Which products and versions are affected?** Bytecode Alliance Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3.

**Is there a fix for CVE-2026-119143?** Yes: fixed in Wasmtime 48.0.6, 49.0.3. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-119143 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-119143?** Check whether you run Bytecode Alliance Wasmtime at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Wasmtime 48.0.6, 49.0.3

## Technical details

The vulnerability exists in Wasmtime's DirectSource and DirectDestination APIs, specifically the remaining method, which fails to validate addresses during zero-length component model stream reads or writes. While the specification permits skipping address validation for zero-length operations, Wasmtime later indexes into guest linear memory without proper bounds checking, causing a panic. This affects all embedders using WASIp3 in the wasmtime-wasi crate or directly using the Direct stream APIs with untrusted guest code.

## Affected products

- Bytecode Alliance Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3

## Timeline

- 2026-10-14: advisory
- 2026-10-29: disclosed

## References

- [https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-93g3-36p8-x2gc](https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-93g3-36p8-x2gc)
- [https://www.vulncheck.com/advisories/wasmtime-46.0.0-before-48.0.6-and-49.0.0-before-49.0.3-panic-via-zero-length-stream-writes](https://www.vulncheck.com/advisories/wasmtime-46.0.0-before-48.0.6-and-49.0.0-before-49.0.3-panic-via-zero-length-stream-writes)

## Related threats

- [Wasmtime wasi-http response splitting via unvalidated headers](https://junglewise.ai/threats/cve-2026-121439-wasmtime-46-0-0-before-48-0-7-and-49-0-0-before-49-0-4-contains)
- [Wasmtime host panic in call_async Future drop](https://junglewise.ai/threats/cve-2026-119142-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)
- [Wasmtime denial of service in realloc handling](https://junglewise.ai/threats/cve-2026-119141-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)
- [Wasmtime denial of service via thread.yield in component start](https://junglewise.ai/threats/cve-2026-119140-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)
- [Wasmtime host crash in async-lifted function invocation](https://junglewise.ai/threats/cve-2026-119139-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)