# CVE-2017-15705: Denial of service in Apache SpamAssassin

> Crafted emails with unclosed tags cause excessive scan times in Apache SpamAssassin, leading to denial of service.

- **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:** 17 Sep 2018
- **Updated:** 16 Sep 2024
- **Also known as:** ALPINE-CVE-2017-15705, DEBIAN-CVE-2017-15705, GHSA-m63q-qrvc-wwrm, UBUNTU-CVE-2017-15705

## What is CVE-2017-15705?

CVE-2017-15705 is a medium-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 17 Sep 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A denial of service vulnerability was identified that exists in Apache SpamAssassin before 3.4.2. The vulnerability arises with certain unclosed tags in emails that cause markup to be handled incorrectly leading to scan timeouts. In Apache SpamAssassin, using HTML::Parser, we setup an object and hook into the begin and end tag event handlers In both cases, the "open" event is immediately followed by a "close" event - even if the tag *does not* close in the HTML being parsed. Because of this, we are missing the "text" event to deal with the object normally. This can cause carefully crafted emails that might take more scan time than expected leading to a Denial of Service. The issue is possibly a bug or design decision in HTML::Parser that specifically impacts the way Apache SpamAssassin uses the module with poorly formed html. The exploit has been seen in the wild but not believed to have been purposefully part of a Denial of Service attempt. We are concerned that there may be attempts to abuse the vulnerability in the future.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2017-15705?

It affects 7 products.


Products: Apache Spamassassin, Canonical Ubuntu Linux, Debian Debian Linux, Redhat Enterprise Linux Desktop, Redhat Enterprise Linux Eus, Redhat Enterprise Linux Server, Redhat Enterprise Linux Workstation.

## How do I fix CVE-2017-15705?

Upgrade to a fixed version.

## Is CVE-2017-15705 being exploited?

There is no known exploitation of CVE-2017-15705 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-1946](https://insights.sbomify.com/CVE-2020-1946/): Apache SpamAssassin has an OS Command Injection vulnerability (critical 9.8)
- [CVE-2018-11780](https://insights.sbomify.com/CVE-2018-11780/): Code injection in Apache SpamAssassin (critical 9.8)
- [CVE-2020-1930](https://insights.sbomify.com/CVE-2020-1930/): Command injection in Apache SpamAssassin (high 8.1)
- [CVE-2020-1931](https://insights.sbomify.com/CVE-2020-1931/): Command injection in Apache SpamAssassin (high 8.1)
- [CVE-2018-11781](https://insights.sbomify.com/CVE-2018-11781/): Apache SpamAssassin 3.4.2 fixes a local user code injection in the meta rule syntax. (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-15705 and fix it if it is affected.

What it is: CVE-2017-15705 is a medium-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 17 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-2017-15705 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-2017-15705/ (Markdown: https://insights.sbomify.com/CVE-2017-15705/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-15705
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-15705
- OSV: https://osv.dev/vulnerability/CVE-2017-15705

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From sbomify Insights: https://insights.sbomify.com/CVE-2017-15705/
Summaries are generated and may contain mistakes; the official description above is the record.