# CVE-2026-48691: Integer overflow in n/a

> An integer overflow in FastNetMon's BGP encoder allows heap buffer overflows, potentially leading to remote code execution or service crashes.

- **Severity:** High 7.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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:** 26 May 2026
- **Updated:** 27 May 2026
- **Also known as:** DEBIAN-CVE-2026-48691, GHSA-pjmc-gjwh-qr2w, UBUNTU-CVE-2026-48691

## What is CVE-2026-48691?

CVE-2026-48691 is a high-severity 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 integer overflow in the BGP AS_PATH attribute encoder. In src/bgp_protocol.hpp, the IPv4UnicastAnnounce::get_attributes() function computes attribute_length as 'sizeof(bgp_as_path_segment_element_t) + this->as_path_asns.size() * sizeof(uint32_t)' and stores it in a uint8_t field (line 600-605). Since uint8_t can only hold values 0-255, an AS_PATH containing more than 63 ASNs (2 + 64*4 = 258 > 255) causes silent truncation. The truncated length is used for buffer sizing, while the actual data written is the full untruncated amount, resulting in a heap buffer overflow. Similarly, the path_segment_length field at line 621 is also uint8_t, truncating with more than 255 ASNs.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-48691?

It affects 1 product.


Products: Pavel-Odintsov Fastnetmon.

## How do I fix CVE-2026-48691?

Upgrade to a fixed version.

## Is CVE-2026-48691 being exploited?

There is no known exploitation of CVE-2026-48691 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-2026-48689](https://insights.sbomify.com/CVE-2026-48689/): 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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48691 and fix it if it is affected.

What it is: CVE-2026-48691 is a high-severity 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-2026-48691 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-2026-48691/ (Markdown: https://insights.sbomify.com/CVE-2026-48691/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48691
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48691
- OSV: https://osv.dev/vulnerability/CVE-2026-48691

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48691/
Summaries are generated and may contain mistakes; the official description above is the record.