---
id: "CVE-2026-115387"
kind: "vulnerability"
aliases: ["CVE-2026-115387"]
title: "Wasmtime: overflowing filesystem timestamps let a guest program crash the host"
severity: "medium"
cvss: 6.9
epss: 0.00112
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["runtime", "self-hosted", "wasi", "wasmtime", "webassembly"]
not_affected_if: ["no-filesystem-wasi", "trusted-guest-only"]
published_at: "2026-10-22T19:17:46+00:00"
first_seen_at: "2026-10-23T21:57:31+00:00"
updated_at: "2026-10-25T03:38:45+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-115387", "first_seen_at": "2026-10-23T21:57:31+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-115387", "first_seen_at": "2026-10-24T07:15:51+00:00"}]
---

# Wasmtime: overflowing filesystem timestamps let a guest program crash the host

Wasmtime's WASI filesystem code panics the host when a guest program passes timestamp values whose sub-second field overflows the seconds field to set-times calls. An attacker running a WASI guest program can crash the host process, causing denial of service.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `wasmtime --version` and compare against the fixed lines: `36.0.16`, `48.0.3`, `49.0.1`
- Check the Cargo.lock of embedding applications for the `wasmtime-wasi` version

## Fix

- Upgrade Wasmtime to `36.0.16`, `48.0.3`, or `49.0.1`, whichever matches your release line
- Rebuild embedding applications so they pick up the patched `wasmtime-wasi`

## Timeline

- 2026-10-23T21:57:31+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-115387
- 2026-10-24T07:15:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-115387

## From the sources

Wasmtime before 36.0.16, 37.0.0 before 48.0.3, and 49.0.0 before 49.0.1 contains a denial of service vulnerability in wasmtime-wasi that allows guest WASI programs to panic the host via overflowing filesystem timestamps. Attackers can pass atim or mtim values whose sub-second field overflows the seconds field to path_filestat_set_times, fd_filestat_set_times, set-times, or set-times-at, crashing the host.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_