# CVE-2026-49494: Xcitium Client Security / Comodo Internet Security Remote Denial of Service

> Remote attackers can crash Windows systems via crafted IPv6 packets due to an integer underflow in the firewall driver, affecting Xcitium and Comodo security products.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Jun 2026
- **Updated:** 23 Jun 2026
- **Also known as:** GHSA-87cf-mxjw-fmjh

## What is CVE-2026-49494?

CVE-2026-49494 is a high-severity vulnerability in Xcitium Comodo Internet Security, published on 7 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Xcitium Client Security (XCS) before 13.8.2.10019 and Comodo Internet Security (CIS) through 12.3.4.8162 (fix expected by 2026 Q3) contain an integer underflow vulnerability in the firewall driver Inspect.sys that allows remote unauthenticated attackers to crash the system by sending a crafted IPv6 packet with a declared payload length smaller than the sum of its extension-header lengths. The unsigned 64-bit payload-length value underflows to a near-maximal integer, triggering an out-of-bounds read and oversized memcpy in the Windows kernel at DISPATCH_LEVEL, resulting in a blue screen of death even on hosts with all ports blocked.

Weakness: CWE-191 (Integer Underflow (Wrap or Wraparound))

## Which versions are affected by CVE-2026-49494?


## How do I fix CVE-2026-49494?

No fix has been published for CVE-2026-49494 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-49494 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49494 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-49494 and fix it if it is affected.

What it is: CVE-2026-49494 is a high-severity vulnerability in Xcitium Comodo Internet Security, published on 7 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49494 exists.

Affected product: Xcitium Comodo Internet Security. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-49494/ (Markdown: https://insights.sbomify.com/CVE-2026-49494/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-49494
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-49494
- OSV: https://osv.dev/vulnerability/CVE-2026-49494

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-49494/
Summaries are generated and may contain mistakes; the official description above is the record.