# CVE-2018-1172: Null dereference in The Squid Software Foundation Squid

> Remote attackers can cause a denial of service in Squid proxy servers by triggering a null pointer dereference via crafted requests.

- **Severity:** Medium 5.9 (`CVSS:3.0/AV:N/AC:H/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:** 16 May 2018
- **Updated:** 5 Aug 2024
- **Also known as:** ALPINE-CVE-2018-1172, DEBIAN-CVE-2018-1172, GHSA-5pj9-pxj3-pc8r, SUSE-SU-2018:1122-1, SUSE-SU-2018:1365-1

## What is CVE-2018-1172?

CVE-2018-1172 is a medium-severity vulnerability in Squid-Cache Squid, published on 16 May 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

This vulnerability allows remote attackers to deny service on vulnerable installations of The Squid Software Foundation Squid 3.5.27-20180318. Authentication is not required to exploit this vulnerability. The specific flaw exists within ClientRequestContext::sslBumpAccessCheck(). A crafted request can trigger the dereference of a null pointer. An attacker can leverage this vulnerability to create a denial-of-service condition to users of the system. Was ZDI-CAN-6088.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2018-1172?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `squid3` | SUSE:Linux Enterprise Server 11 SP4 | All versions | 3.1.23-8.16.37.6.1 |
| `squid` | SUSE:Linux Enterprise Server 12 SP3 | All versions | 3.5.21-26.9.1 |
| `squid3` | SUSE:Linux Enterprise Server for SAP Applications 11 SP4 | All versions | 3.1.23-8.16.37.6.1 |
| `squid` | SUSE:Linux Enterprise Server for SAP Applications 12 SP3 | All versions | 3.5.21-26.9.1 |

Products: Squid-Cache Squid.

## How do I fix CVE-2018-1172?

Apply the vendor's patch.

## Is CVE-2018-1172 being exploited?

There is no known exploitation of CVE-2018-1172 in the wild and no public exploit code.

## 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-2018-1172 and fix it if it is affected.

What it is: CVE-2018-1172 is a medium-severity vulnerability in Squid-Cache Squid, published on 16 May 2018. 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-2018-1172 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-2018-1172/ (Markdown: https://insights.sbomify.com/CVE-2018-1172/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-1172
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-1172
- OSV: https://osv.dev/vulnerability/CVE-2018-1172

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-1172/
Summaries are generated and may contain mistakes; the official description above is the record.