CVE-2026-91949: freerdp Protection Mechanism Failure
Vulnerability summary
CVE-2026-91949 is a critical (CVSS 9.3) Protection Mechanism Failure vulnerability in freerdp. EPSS estimates a 0.56% chance of exploitation in the next 30 days, higher than 45.9% of scored vulnerabilities. 1 public exploit is recorded.
Advisory lineage
Upstream 0 · Downstream 1Timeline
- 15-09-2026PublishedVulnerability first disclosed.
- 17-09-2026Last modifiedVulnerability information updated.
Description
FreeRDP server versions before 3.31.0 contain a protocol negotiation bypass vulnerability that allows unauthenticated attackers to establish RDSTLS connections despite server policy disabling them. Attackers can send incompatible protocol requests, receive negotiation failures, then complete TLS handshake and enter RDSTLS to bypass pre-authentication transport restrictions.
CVSS metrics
8 scores · 5 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated9.2CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N
- OSV · DebianEcosystem advisory · calculated9.2CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- NVDNIST9.2CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- OSV · Red hatEcosystem advisory · calculated9.3CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
- OSV · UbuntuEcosystem advisory · calculated9.3CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
- NVDNIST9.3CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
EPSS trend
Probability
0.56%
Chance of exploitation in the next 30 days
Percentile
46%
Versus all other CVEs
30-day change
+0.12 pp
From 0.45% on 21-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundFreerdp
Maturity: poc
Weaknesses
CWE · root causeAffected systems
Redhat11 products
- freerdp< 2:3.10.3-12.el10_2.13
- freerdp-debuginfo< 2:3.10.3-12.el10_2.13
- freerdp-debugsource< 2:3.10.3-12.el10_2.13
- freerdp-devel< 2:3.10.3-12.el10_2.13
- freerdp-libs< 2:3.10.3-12.el10_2.13
Ubuntu3 products
- freerdpAll versions (No fix recorded)
- freerdp2All versions (No fix recorded)
- freerdp3< 3.31.0+dfsg-0ubuntu0.24.04.1 | < 3.31.0+dfsg-0ubuntu0.26.04.1
Debian1 product
- freerdp3All versions (No fix recorded) | < 3.31.0+dfsg-1
Freerdp1 product
- freerdp≥ 3.0.0, < 3.31.0
4 vendors · 16 products
References
12 links- github.com/FreeRDP/FreeRDP/security/advisories/GHSA-x7v6-xfx3-52j6Vendor AdvisoryARTICLEREPORTExploitMitigation
- www.vulncheck.com/advisories/freerdp-3.0.0-through-3.30.0-protocol-negotiation-bypassThird Party AdvisoryARTICLE
