# CVE-2021-43173: Hanging RRDP request

> An attacker can stall RPKI validation by slowly drip-feeding data, causing Routinator to serve stale data or fail to start.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Nov 2021
- **Updated:** 16 Sep 2024
- **Also known as:** DEBIAN-CVE-2021-43173, GHSA-pgwq-8wjv-xhhr, UBUNTU-CVE-2021-43173

## What is CVE-2021-43173?

CVE-2021-43173 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 9 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In NLnet Labs Routinator prior to 0.10.2, a validation run can be delayed significantly by an RRDP repository by not answering but slowly drip-feeding bytes to keep the connection alive. This can be used to effectively stall validation. While Routinator has a configurable time-out value for RRDP connections, this time-out was only applied to individual read or write operations rather than the complete request. Thus, if an RRDP repository sends a little bit of data before that time-out expired, it can continuously extend the time it takes for the request to finish. Since validation will only continue once the update of an RRDP repository has concluded, this delay will cause validation to stall, leading to Routinator continuing to serve the old data set or, if in the initial validation run directly after starting, never serve any data at all.

Weakness: CWE-400 (Uncontrolled Resource Consumption), CWE-755 (Improper Handling of Exceptional Conditions)

## Which versions are affected by CVE-2021-43173?

It affects 2 products.


Products: Debian Debian Linux, Nlnetlabs Routinator.

## How do I fix CVE-2021-43173?

Upgrade to a fixed version.

## Is CVE-2021-43173 being exploited?

There is no known exploitation of CVE-2021-43173 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43173 and fix it if it is affected.

What it is: CVE-2021-43173 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 9 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-43173 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2021-43173/ (Markdown: https://insights.sbomify.com/CVE-2021-43173/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43173
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43173
- OSV: https://osv.dev/vulnerability/CVE-2021-43173

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43173/
Summaries are generated and may contain mistakes; the official description above is the record.