# CVE-2026-48689: Memory corruption in n/a

> An off-by-one heap buffer overflow in FastNetMon allows remote attackers to achieve arbitrary code execution via crafted network traffic.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 May 2026
- **Updated:** 27 May 2026
- **Also known as:** DEBIAN-CVE-2026-48689, GHSA-5444-f65m-f3c8, UBUNTU-CVE-2026-48689

## What is CVE-2026-48689?

CVE-2026-48689 is a critical memory corruption vulnerability in n/a, published on 26 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

FastNetMon Community Edition through 1.2.9 contains an off-by-one heap-based buffer overflow in the dynamic_binary_buffer_t class (src/dynamic_binary_buffer.hpp). Five methods (append_dynamic_buffer, append_data_as_pointer, append_data_as_object_ptr, memcpy_from_ptr, memcpy_from_object_ptr) use an incorrect bounds check of the form 'if (offset + length > maximum_internal_storage_size + 1)' instead of the correct 'if (offset + length > maximum_internal_storage_size)'. This allows writing exactly one byte past the end of the heap-allocated buffer. The class is used pervasively in BGP message encoding/decoding, NetFlow template processing, and Flow Spec NLRI construction. An attacker who can send network traffic (NetFlow, sFlow, IPFIX, or BGP) to a FastNetMon instance can trigger this overflow, potentially achieving arbitrary code execution by corrupting heap metadata. Notably, the append_byte() method uses the correct bounds check, confirming the inconsistency.

Weakness: CWE-787 (Out-of-bounds Write), CWE-193 (Off-by-one Error), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-48689?

It affects 1 product.


Products: Pavel-Odintsov Fastnetmon.

## How do I fix CVE-2026-48689?

Upgrade to a fixed version.

## Is CVE-2026-48689 being exploited?

There is no known exploitation of CVE-2026-48689 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2026-48686](https://insights.sbomify.com/CVE-2026-48686/): Memory corruption in n/a (critical 9.8)
- [CVE-2026-48687](https://insights.sbomify.com/CVE-2026-48687/): Command injection in n/a (high 8.1)
- [CVE-2026-48692](https://insights.sbomify.com/CVE-2026-48692/): Missing authorization in n/a (high 8.1)
- [CVE-2026-48694](https://insights.sbomify.com/CVE-2026-48694/): Command injection in n/a (high 8.1)
- [CVE-2026-48695](https://insights.sbomify.com/CVE-2026-48695/): Command injection in n/a (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48689 and fix it if it is affected.

What it is: CVE-2026-48689 is a critical memory corruption vulnerability in n/a, published on 26 May 2026. 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-2026-48689 in the wild and no public exploit code.

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-2026-48689/ (Markdown: https://insights.sbomify.com/CVE-2026-48689/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48689
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48689
- OSV: https://osv.dev/vulnerability/CVE-2026-48689

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48689/
Summaries are generated and may contain mistakes; the official description above is the record.