# CVE-2026-18238: OOBR in rpcap client in libpcap before 1.10.7

> A malicious RPCAP server can trigger an out-of-bounds read in libpcap, potentially leaking memory or causing a crash.

- **Severity:** Medium 5.0 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** AZL-99729, AZL-99927, DEBIAN-CVE-2026-18238, ECHO-bc26-fe28-c8e1, GHSA-2xr5-28gv-34j3, UBUNTU-CVE-2026-18238

## What is CVE-2026-18238?

CVE-2026-18238 is a medium-severity memory corruption vulnerability in The Tcpdump Group libpcap, published on 5 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The rpcap client code that processes a RPCAP_MSG_PACKET message received from the server incorrectly validates its headers.  A malicious server can send a crafted message and cause the client to treat up to 20 bytes of the client process memory beyond the end of the buffer as if it was a part of the captured packet.

Weakness: CWE-1288 (Improper Validation of Consistency within Input), CWE-126 (Buffer Over-read)

## Which versions are affected by CVE-2026-18238?


## How do I fix CVE-2026-18238?

Upgrade to a fixed version.

## Is CVE-2026-18238 being exploited?

There is no known exploitation of CVE-2026-18238 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18238 and fix it if it is affected.

What it is: CVE-2026-18238 is a medium-severity memory corruption vulnerability in The Tcpdump Group libpcap, published on 5 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-18238 in the wild and no public exploit code.

Affected product: The Tcpdump Group libpcap. 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-2026-18238/ (Markdown: https://insights.sbomify.com/CVE-2026-18238/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18238
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18238
- OSV: https://osv.dev/vulnerability/CVE-2026-18238

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18238/
Summaries are generated and may contain mistakes; the official description above is the record.