# CVE-2021-34698: Cisco Web Security Appliance Proxy Service Denial of Service Vulnerability

> Unauthenticated remote attackers can cause a denial of service on Cisco Web Security Appliances by exhausting system memory via numerous HTTPS connections.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Oct 2021
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-vj66-rqm3-j78p

## What is CVE-2021-34698?

CVE-2021-34698 is a high-severity denial of service vulnerability in Cisco Asyncos, published on 6 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the proxy service of Cisco AsyncOS for Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to exhaust system memory and cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper memory management in the proxy service of an affected device. An attacker could exploit this vulnerability by establishing a large number of HTTPS connections to the affected device. A successful exploit could allow the attacker to cause the system to stop processing new connections, which could result in a DoS condition. Note: Manual intervention may be required to recover from this situation.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2021-34698?

It affects 1 product.


Products: Cisco Asyncos.

## How do I fix CVE-2021-34698?

No fix has been published for CVE-2021-34698 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34698 being exploited?

There is no known exploitation of CVE-2021-34698 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Asyncos

- [CVE-2025-20393](https://insights.sbomify.com/CVE-2025-20393/): Cisco Multiple Products Improper Input Validation (critical 10.0, exploited in the wild)
- [CVE-2026-76519](https://insights.sbomify.com/CVE-2026-76519/): Cisco Secure Email Gateway Relative Path Traversal (critical 9.8, exploited in the wild)
- [CVE-2026-76461](https://insights.sbomify.com/CVE-2026-76461/): Cisco Secure Email Gateway SQL Injection (critical 9.8, exploited in the wild)
- [CVE-2024-20435](https://insights.sbomify.com/CVE-2024-20435/): Command injection in Cisco Secure Web Appliance (high 8.8)
- [CVE-2019-15956](https://insights.sbomify.com/CVE-2019-15956/): Cisco Web Security Appliance Unauthorized Device Reset Vulnerability (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34698 and fix it if it is affected.

What it is: CVE-2021-34698 is a high-severity denial of service vulnerability in Cisco Asyncos, published on 6 Oct 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-2021-34698 in the wild and no public exploit code.

Affected product: Cisco Asyncos. 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-2021-34698/ (Markdown: https://insights.sbomify.com/CVE-2021-34698/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34698
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34698
- OSV: https://osv.dev/vulnerability/CVE-2021-34698

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-34698/
Summaries are generated and may contain mistakes; the official description above is the record.