# CVE-2026-20311: Cisco IOS XE Software Web UI Denial of Service Vulnerability

> An authenticated low-privilege attacker can cause a denial of service on Cisco IOS XE devices by submitting a malformed certificate to the web UI.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Aug 2026
- **Updated:** 5 Aug 2026
- **Also known as:** GHSA-7wh7-mfpx-74m2

## What is CVE-2026-20311?

CVE-2026-20311 is a medium-severity denial of service vulnerability in Cisco IOS XE Software, published on 5 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A vulnerability in the web-based management interface of Cisco IOS XE Software could allow an authenticated, remote attacker with low privileges to cause a denial of service (DoS) condition on an affected device.

This vulnerability is due to insufficient error handling in the web-based management interface. An attacker could exploit this vulnerability by authenticating with a malformed certificate. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.

Weakness: CWE-126 (Buffer Over-read)

## Which versions are affected by CVE-2026-20311?


## How do I fix CVE-2026-20311?

No fix has been published for CVE-2026-20311 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-20311 being exploited?

There is no known exploitation of CVE-2026-20311 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20311 and fix it if it is affected.

What it is: CVE-2026-20311 is a medium-severity denial of service vulnerability in Cisco IOS XE Software, published on 5 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-20311 in the wild and no public exploit code.

Affected product: Cisco IOS XE Software. 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-2026-20311/ (Markdown: https://insights.sbomify.com/CVE-2026-20311/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20311
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20311
- OSV: https://osv.dev/vulnerability/CVE-2026-20311

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-20311/
Summaries are generated and may contain mistakes; the official description above is the record.