HIGH CVSS 7.5
Published: 2026-02-24

CVE-2026-27195

bytecodealliance wasmtime Security Advisory (CVE-2026-27195)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-27195 impacting bytecodealliance wasmtime. Evaluated with CVSS Base Score of 7.5 (HIGH).

Original NVD Description

Source: NIST NVD
Wasmtime is a runtime for WebAssembly. Starting with Wasmtime 39.0.0, the `component-model-async` feature became the default, which brought with it a new implementation of `[Typed]Func::call_async` which made it capable of calling async-typed guest export functions. However, that implementation had a bug leading to a panic under certain circumstances: First, the host embedding calls `[Typed]Func::call_async` on a function exported by a component, polling the returned `Future` once. Second, the component function yields control to the async runtime (e.g. Tokio), e.g. due to a call to host function registered using `LinkerInstance::func_wrap_async` which yields, or due an epoch interruption. Third, the host embedding drops the `Future` after polling it once. This leaves the component instance in a non-reenterable state since the call never had a chance to complete. Fourth, the host embedding calls `[Typed]Func::call_async` again, polling the returned `Future`. Since the component instance cannot be entered at this point, the call traps, but not before allocating a task and thread for the call. Fifth, the host embedding ignores the trap and drops the `Future`. This panics due to the runtime attempting to dispose of the task created above, which panics since the thread has not yet exited. When a host embedder using the affected versions of Wasmtime calls `wasmtime::component::[Typed]Func::call_async` on a guest export and then drops the returned future without waiting for it to resolve, and then does so again with the same component instance, Wasmtime will panic. Embeddings that have the `component-model-async` compile-time feature disabled are unaffected. Wasmtime 40.0.4 and 41.0.4 have been patched to fix this issue. Versions 42.0.0 and later are not affected. If an embedding is not actually using any component-model-async features then disabling the `component-model-async` Cargo feature can work around this issue. This issue can also be worked around by either ensuring every `call_async` future is awaited until it completes or refraining from using the `Store` again after dropping a not-yet-resolved `call_async` future.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
None (I:N)
No system modification impact
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product bytecodealliance / wasmtime
Affected Versions *
Weakness Enumeration CWE-755

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2026-27195 impacting bytecodealliance wasmtime.

⚡ Nuclei Detection Template (YAML) cve-2026-27195.yaml
id: cve-2026-27195

info:
  name: bytecodealliance wasmtime - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-27195 affecting bytecodealliance wasmtime.
    Evaluation: Wasmtime is a runtime for WebAssembly. Starting with Wasmtime 39.0.0, the `component-model-async` feature became the default, which brought with it a ...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-27195
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    cvss-score: 7.5
    cve-id: CVE-2026-27195
    cwe-id: CWE-755
  tags: cve,cve-2026-27195,bytecodealliance,wasmtime,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "wasmtime"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-27195.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-27195
# Target: bytecodealliance wasmtime | CVSS: 7.5 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-27195 (bytecodealliance wasmtime)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against bytecodealliance wasmtime scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2026-27195.sh
# Recommended Remediation & Patching Commands for CVE-2026-27195
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install wasmtime 2>/dev/null || \
sudo dnf upgrade wasmtime 2>/dev/null || \
sudo yum update wasmtime

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i wasmtime 2>/dev/null || rpm -qa | grep -i wasmtime

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-27195 in bytecodealliance wasmtime?

Review vendor-specific security notices and update bytecodealliance wasmtime packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2026-27195?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2026-27195?

CVE-2026-27195 is classified with a CVSS 3.1 Base Score of 7.5 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.5
HIGH SEVERITY
CVE ID CVE-2026-27195
Weakness CWE-755
Vendor bytecodealliance
Product wasmtime
Published 2026-02-24
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H