# CVE-2018-14647: Denial of service in Python

> Attackers can cause denial of service in Python applications by sending crafted XML documents that trigger hash collisions in the Expat parser.

- **Severity:** Medium 5.3 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2018
- **Updated:** 7 Oct 2026
- **Also known as:** ALPINE-CVE-2018-14647, DEBIAN-CVE-2018-14647, GHSA-gvw2-fvqg-v8mm, PSF-2018-5, SUSE-SU-2018:3156-1, UBUNTU-CVE-2018-14647

## What is CVE-2018-14647?

CVE-2018-14647 is a medium-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 25 Sep 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Python's elementtree C accelerator failed to initialise Expat's hash salt during initialization. This could make it easy to conduct denial of service attacks against Expat by constructing an XML document that would cause pathological hash collisions in Expat's internal data structures, consuming large amounts CPU and RAM. The vulnerability exists in Python versions 3.7.0, 3.6.0 through 3.6.6, 3.5.0 through 3.5.6, 3.4.0 through 3.4.9, 2.7.0 through 2.7.15.

Weakness: CWE-909 (Missing Initialization of Resource), CWE-665 (Improper Initialization), CWE-335 (Incorrect Usage of Seeds in Pseudo-Random Number Generator (PRNG))

## Which versions are affected by CVE-2018-14647?

It affects 8 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `python` | SUSE:Linux Enterprise Server 11 SP4 | All versions | 2.6.9-40.21.2 |
| `python-base` | SUSE:Linux Enterprise Server 11 SP4 | All versions | 2.6.9-40.21.1 |
| `python-doc` | SUSE:Linux Enterprise Server 11 SP4 | All versions | 2.6-8.40.21.1 |
| `python` | SUSE:Linux Enterprise Server for SAP Applications 11 SP4 | All versions | 2.6.9-40.21.2 |
| `python-base` | SUSE:Linux Enterprise Server for SAP Applications 11 SP4 | All versions | 2.6.9-40.21.1 |
| `python-doc` | SUSE:Linux Enterprise Server for SAP Applications 11 SP4 | All versions | 2.6-8.40.21.1 |
| `python` | SUSE:Linux Enterprise Software Development Kit 11 SP4 | All versions | 2.6.9-40.21.2 |
| `python-base` | SUSE:Linux Enterprise Software Development Kit 11 SP4 | All versions | 2.6.9-40.21.1 |
| `python-doc` | SUSE:Linux Enterprise Software Development Kit 11 SP4 | All versions | 2.6-8.40.21.1 |

Products: Canonical Ubuntu Linux, Debian Debian Linux, Fedoraproject Fedora, Opensuse Leap, Python Python, Redhat Enterprise Linux Desktop, Redhat Enterprise Linux Server, Redhat Enterprise Linux Workstation.

## How do I fix CVE-2018-14647?

Upgrade to a fixed version.

## Is CVE-2018-14647 being exploited?

There is no known exploitation of CVE-2018-14647 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-14647 and fix it if it is affected.

What it is: CVE-2018-14647 is a medium-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 25 Sep 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-2018-14647 in the wild and no public exploit code.

Affected product: Canonical Ubuntu 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-2018-14647/ (Markdown: https://insights.sbomify.com/CVE-2018-14647/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-14647
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-14647
- OSV: https://osv.dev/vulnerability/CVE-2018-14647

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-14647/
Summaries are generated and may contain mistakes; the official description above is the record.