# CVE-2008-1637: Weak cryptography in n/a

> Remote attackers can poison the DNS cache due to insufficient randomness in transaction IDs and source ports, affecting PowerDNS Recursor users.

- **Severity:** Medium 6.8 (`AV:N/AC:M/Au:N/C:P/I:P/A:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Apr 2008
- **Updated:** 7 Aug 2024
- **Also known as:** DEBIAN-CVE-2008-1637, DSA-1544-1, GHSA-c5qh-3289-h9w4

## What is CVE-2008-1637?

CVE-2008-1637 is a medium-severity vulnerability in Powerdns Recursor, published on 2 Apr 2008. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

PowerDNS Recursor before 3.1.5 uses insufficient randomness to calculate (1) TRXID values and (2) UDP source port numbers, which makes it easier for remote attackers to poison a DNS cache, related to (a) algorithmic deficiencies in rand and random functions in external libraries, (b) use of a 32-bit seed value, and (c) choice of the time of day as the sole seeding information.

Weakness: CWE-189

## Which versions are affected by CVE-2008-1637?

It affects 1 product.


Products: Powerdns Recursor.

## How do I fix CVE-2008-1637?

Upgrade to a fixed version.

## Is CVE-2008-1637 being exploited?

There is no known exploitation of CVE-2008-1637 in the wild and no public exploit code.

## Other vulnerabilities in Powerdns Recursor

- [CVE-2009-4009](https://insights.sbomify.com/CVE-2009-4009/): Memory corruption in n/a (critical 10.0)
- [CVE-2020-10030](https://insights.sbomify.com/CVE-2020-10030/): Memory corruption in n/a (high 8.8)
- [CVE-2025-59023](https://insights.sbomify.com/CVE-2025-59023/): Crafted delegations or IP fragments can poison cached delegations in Recursor (high 8.2)
- [CVE-2025-59030](https://insights.sbomify.com/CVE-2025-59030/): Insufficient validation of incoming notifies over TCP can lead to a denial of service in Recursor (high 7.5)
- [CVE-2023-22617](https://insights.sbomify.com/CVE-2023-22617/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2008-1637 and fix it if it is affected.

What it is: CVE-2008-1637 is a medium-severity vulnerability in Powerdns Recursor, published on 2 Apr 2008. 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-2008-1637 in the wild and no public exploit code.

Affected product: Powerdns Recursor. 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-2008-1637/ (Markdown: https://insights.sbomify.com/CVE-2008-1637/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2008-1637
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2008-1637
- OSV: https://osv.dev/vulnerability/CVE-2008-1637

---
From sbomify Insights: https://insights.sbomify.com/CVE-2008-1637/
Summaries are generated and may contain mistakes; the official description above is the record.