# CVE-2016-2569: Denial of service in n/a

> Remote servers can cause a denial of service in Squid proxy via crafted HTTP headers, requiring an upgrade to fix.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/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:** Yes
- **Published:** 27 Feb 2016
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-6gm6-3v5f-xfhg, UBUNTU-CVE-2016-2569

## What is CVE-2016-2569?

CVE-2016-2569 is a high-severity denial of service vulnerability in Squid-Cache Squid, published on 27 Feb 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Squid 3.x before 3.5.15 and 4.x before 4.0.7 does not properly append data to String objects, which allows remote servers to cause a denial of service (assertion failure and daemon exit) via a long string, as demonstrated by a crafted HTTP Vary header.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2016-2569?

It affects 1 product.


Products: Squid-Cache Squid.

## How do I fix CVE-2016-2569?

Upgrade to a fixed version.

## Is CVE-2016-2569 being exploited?

There is no known exploitation of CVE-2016-2569 in the wild and no public exploit code.

Public exploit code:

- Squid 3.x before 3.5.15 and 4.x before 4.0.7 does not properly append data to String objects, which allows remote servers to cause a denial of service (assertion failure and daemon exit) via a long string, as demonstrated by a crafted HTTP Vary header. (github_poc): https://github.com/amit-raut/CVE-2016-2569

## Other vulnerabilities in Squid-Cache Squid

- [CVE-2025-62168](https://insights.sbomify.com/CVE-2025-62168/): Squid vulnerable to information disclosure via authentication credential leakage in error handling (critical 10.0)
- [CVE-2025-54574](https://insights.sbomify.com/CVE-2025-54574/): Squid's URN Handling can lead to Buffer Overflow (critical 9.3)
- [CVE-2026-33526](https://insights.sbomify.com/CVE-2026-33526/): Squid vulnerable to Denial of Service in ICP Request handling (critical 9.2)
- [CVE-2026-32748](https://insights.sbomify.com/CVE-2026-32748/): Squid has Denial of Service in ICP Response handling (high 8.7)
- [CVE-2023-50269](https://insights.sbomify.com/CVE-2023-50269/): SQUID-2023:10 Denial of Service in HTTP Request parsing (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-2569 and fix it if it is affected.

What it is: CVE-2016-2569 is a high-severity denial of service vulnerability in Squid-Cache Squid, published on 27 Feb 2016. 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-2016-2569 in the wild and no public exploit code.

Affected product: Squid-Cache Squid. 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-2016-2569/ (Markdown: https://insights.sbomify.com/CVE-2016-2569/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-2569
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-2569
- OSV: https://osv.dev/vulnerability/CVE-2016-2569

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-2569/
Summaries are generated and may contain mistakes; the official description above is the record.