# CVE-2026-115387: Wasmtime denial of service via WASI filesystem timestamp overflow

Source: https://junglewise.ai/threats/cve-2026-115387-wasmtime-before-36-0-16-37-0-0-before-48-0-3-and-49-0-0-before  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-22. Updated: 2026-10-22  
License: CC BY 4.0 with a link back

CVE-2026-115387 · Severity: medium · CVSS 6.2 · Published 2026-10-22

Wasmtime is a WebAssembly runtime that executes untrusted code in isolated environments. A guest WASM program can crash the entire host runtime by passing specially crafted filesystem timestamp values to file operations, causing a denial of service that halts all workloads.

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-2026-115387 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-115387 being exploited in the wild.

**How severe is CVE-2026-115387?** Medium severity, with a CVSS score of 6.2, published 22 October 2026.

**Which products and versions are affected?** Bytecode Alliance Wasmtime before 36.0.16, 37.0.0 before 48.0.3, 49.0.0 before 49.0.1.

**Is there a fix for CVE-2026-115387?** Yes: fixed in 36.0.16, 48.0.3, 49.0.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-115387 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-115387?** 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 36.0.16, 48.0.3, 49.0.1

## Technical details

The wasmtime-wasi crate fails to validate filesystem timestamp arguments (atim, mtim) before passing them to Rust's std::time::Duration::new, which panics on integer overflow when the microseconds field overflows into the seconds field. An attacker-controlled guest WASM program can trigger this panic by invoking path_filestat_set_times, fd_filestat_set_times, set-times, or set-times-at with overflow values like Timestamp { seconds: u64::MAX, microseconds: 1_000_000_000 }.

## Affected products

- Bytecode Alliance Wasmtime before 36.0.16, 37.0.0 before 48.0.3, 49.0.0 before 49.0.1

## Timeline

- 2026-09-24: disclosed
- 2026-10-22: advisory

## References

- [https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-j2g9-4prp-pf6h](https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-j2g9-4prp-pf6h)
- [https://www.vulncheck.com/advisories/wasmtime-before-36.0.16-37.0.0-before-48.0.3-and-49.0.0-before-49.0.1-host-panic-via-wasi-filesystem-timestamp-overflow](https://www.vulncheck.com/advisories/wasmtime-before-36.0.16-37.0.0-before-48.0.3-and-49.0.0-before-49.0.1-host-panic-via-wasi-filesystem-timestamp-overflow)

## 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 denial of service in component model stream operations](https://junglewise.ai/threats/cve-2026-119143-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-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)