# CVE-2005-0021: Memory corruption in n/a

> Buffer overflows in Exim allow remote attackers to execute arbitrary code via crafted IPv6 addresses or DNS lookups.

- **Severity:** High 7.2 (`AV:L/AC:L/Au:N/C:C/I:C/A:C`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Jan 2005
- **Updated:** 7 Aug 2024
- **Also known as:** DEBIAN-CVE-2005-0021, DSA-635-1, DSA-637-1, GHSA-4wq7-f94f-64w2

## What is CVE-2005-0021?

CVE-2005-0021 is a high-severity memory corruption vulnerability in n/a, published on 6 Jan 2005. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Multiple buffer overflows in Exim before 4.43 may allow attackers to execute arbitrary code via (1) an IPv6 address with more than 8 components, as demonstrated using the -be command line option, which triggers an overflow in the host_aton function, or (2) the -bh command line option or dnsdb PTR lookup, which triggers an overflow in the dns_build_reverse function.

## Which versions are affected by CVE-2005-0021?

It affects 1 product.


Products: University of Cambridge Exim.

## How do I fix CVE-2005-0021?

Upgrade to a fixed version.

## Is CVE-2005-0021 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2005-0021 exists.

Public exploit code:

- Exim 4.41 - 'dns_build_reverse' Local Buffer Overflow (exploitdb)
- Exim 4.41 - 'dns_build_reverse' Local Read Emails (exploitdb)

## Other vulnerabilities in n/a

- [CVE-2004-0399](https://insights.sbomify.com/CVE-2004-0399/): Memory corruption in n/a (high 7.5)
- [CVE-2004-0400](https://insights.sbomify.com/CVE-2004-0400/): Memory corruption in n/a (high 7.5)
- [CVE-2003-0743](https://insights.sbomify.com/CVE-2003-0743/): Memory corruption in n/a (high 7.5)
- [CVE-2002-1381](https://insights.sbomify.com/CVE-2002-1381/): Code injection in n/a (high 7.2)
- [CVE-1999-0971](https://insights.sbomify.com/CVE-1999-0971/): Memory corruption in n/a (high 7.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2005-0021 and fix it if it is affected.

What it is: CVE-2005-0021 is a high-severity memory corruption vulnerability in n/a, published on 6 Jan 2005. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2005-0021 exists.

Affected product: n/a. 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-2005-0021/ (Markdown: https://insights.sbomify.com/CVE-2005-0021/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2005-0021
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2005-0021
- OSV: https://osv.dev/vulnerability/CVE-2005-0021

---
From sbomify Insights: https://insights.sbomify.com/CVE-2005-0021/
Summaries are generated and may contain mistakes; the official description above is the record.