# CVE-2026-90808: HKUDS nanobot ExecTool shell.py ExecTool._spawn incomplete blacklist

> Incomplete command blacklist in nanobot ExecTool allows remote attackers to execute arbitrary shell commands.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X`)
- **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:** 14 Sep 2026
- **Updated:** 14 Sep 2026
- **Also known as:** GHSA-vwc9-2889-5p3f

## What is CVE-2026-90808?

CVE-2026-90808 is a medium-severity command injection vulnerability in HKUDS nanobot, published on 14 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A vulnerability was determined in HKUDS nanobot up to 0.2.1. Impacted is the function ExecTool._guard_command/ExecTool._spawn of the file nanobot/agent/tools/shell.py of the component ExecTool. This manipulation causes incomplete blacklist. It is possible to initiate the attack remotely. Patch name: af582246f141311d574551b7571a517bcc3df750. Applying a patch is the recommended action to fix this issue.

Weakness: CWE-184 (Incomplete List of Disallowed Inputs), CWE-183 (Permissive List of Allowed Inputs)

## Which versions are affected by CVE-2026-90808?


## How do I fix CVE-2026-90808?

No fix has been published for CVE-2026-90808 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-90808 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-90808 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90808 and fix it if it is affected.

What it is: CVE-2026-90808 is a medium-severity command injection vulnerability in HKUDS nanobot, published on 14 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-90808 exists.

Affected product: HKUDS nanobot. 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-2026-90808/ (Markdown: https://insights.sbomify.com/CVE-2026-90808/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90808
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90808
- OSV: https://osv.dev/vulnerability/CVE-2026-90808

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-90808/
Summaries are generated and may contain mistakes; the official description above is the record.