# CVE-2018-19131: Cross-site scripting in n/a

> An attacker can execute arbitrary scripts in the victim's browser via a crafted X.509 certificate during Squid proxy error page generation.

- **Severity:** Medium 6.1 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 9 Nov 2018
- **Updated:** 16 Sep 2024
- **Also known as:** CVE-2018-1000819, DEBIAN-CVE-2018-19131, GHSA-jr78-3r97-gpxf, SUSE-SU-2018:3790-1

## What is CVE-2018-19131?

CVE-2018-19131 is a medium-severity cross-site scripting vulnerability in Squid-Cache Squid, published on 9 Nov 2018. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Squid before 4.4 has XSS via a crafted X.509 certificate during HTTP(S) error page generation for certificate errors.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2018-19131?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `squid3` | SUSE:Linux Enterprise Server 11 SP4 | All versions | 3.1.23-8.16.37.9.1 |
| `squid3` | SUSE:Linux Enterprise Server for SAP Applications 11 SP4 | All versions | 3.1.23-8.16.37.9.1 |

Products: Squid-Cache Squid.

## How do I fix CVE-2018-19131?

Upgrade to a fixed version.

## Is CVE-2018-19131 being exploited?

There is no known exploitation of CVE-2018-19131 in the wild and no public exploit code.

Public exploit code:

- Proof-of-Concept exploit of CVE-2018-19131: Squid Proxy XSS via X.509 Certificate (github_poc): https://github.com/JonathanWilbur/CVE-2018-19131

## 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-2018-19131 and fix it if it is affected.

What it is: CVE-2018-19131 is a medium-severity cross-site scripting vulnerability in Squid-Cache Squid, published on 9 Nov 2018. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2018-19131 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-2018-19131/ (Markdown: https://insights.sbomify.com/CVE-2018-19131/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-19131
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-19131
- OSV: https://osv.dev/vulnerability/CVE-2018-19131

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-19131/
Summaries are generated and may contain mistakes; the official description above is the record.