What is CVE-2026-91964?
FreeRDP versions before 3.31.0 contain a heap-based buffer overflow in nego_send_negotiation_request when processing Server Redirection PDU messages with attacker-controlled LoadBalanceInfo fields. A malicious RDP server can trigger the overflow by sending an arbitrary-length field that gets written to a fixed 512-byte buffer without validation, causing client crashes or potential code execution when chained with memory disclosure.
The record classifies CVE-2026-91964 under weakness class CWE-122. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 61 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 8.8 — HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - CVSS v4.0 base score
- 8.7
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N - EPSS (FIRST)
- 0.6% probability of exploitation in the next 30 days, higher than 49.4% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 8.4/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-09-15
Is CVE-2026-91964 being exploited?
Weaponised exploit code for CVE-2026-91964 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.
- trickest/cve (trickest)
Affected products and versions
- FreeRDP: FreeRDP
How to fix CVE-2026-91964
Vendor advisory: https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-2vf2-grvj-6g8x. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-91964
1 tracked threat in the Threadlinqs corpus references CVE-2026-91964, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories.