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CVE Record

CVE-2026-31806: FreeRDP has a Heap Buffer Overflow in nsc_process_message() via Unchecked SURFACE_BITS_COMMAND Bitmap Dimensions

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.24.0, the gdi_surface_bits() function processes SURFACE_BITS_COMMAND messages sent by the RDP server. When the command is handled using NSCodec, the bmp.width and bmp.height values provided by the server are not properly validated against the actual desktop dimensions. A malicious RDP server can supply crafted bmp.width and bmp.height values that exceed the expected surface size. Because these values are used during bitmap decoding and memory operations without proper bounds checking, this can lead to a heap buffer overflow. Since the attacker can also control the associated pixel data transmitted by the server, the overflow may be exploitable to overwrite adjacent heap memory. This vulnerability is fixed in 3.24.0.

CriticalCVSS 9.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

FreeRDP before 3.24.0 can be crashed or potentially compromised by a malicious RDP server sending malformed bitmap data. The risk is serious because the server controls dimensions and pixel data used in memory operations. The documented fix is FreeRDP 3.24.0 or vendor-supplied patched packages.

Executive priority

Treat as urgent for environments using FreeRDP, especially privileged remote administration workstations. The issue is critical memory corruption reachable from a malicious RDP server, with an available upstream fix. No source in the bundle confirms active exploitation.

Technical view

In NSCodec handling of SURFACE_BITS_COMMAND, gdi_surface_bits() accepts server-provided bmp.width and bmp.height without properly checking them against desktop dimensions. Those values reach bitmap decoding and memory operations, causing a heap buffer overflow in the nsc_process_message() path. The CVE cites CWE-122 and CWE-131, CVSS 4.0 score 9.3, fixed in 3.24.0.

Likely exposure

Exposure is likely where FreeRDP earlier than 3.24.0 is installed or packaged, especially clients connecting to RDP servers outside trusted control. Red Hat published multiple related advisories, so Linux fleet package status should be checked through vendor channels.

Exploitation context

The bundle does not cite active exploitation, and KEV is false. The described attacker is a malicious RDP server sending crafted SURFACE_BITS_COMMAND bitmap dimensions and associated pixel data. The sources state adjacent heap memory may be overwritten, but do not confirm public exploit availability.

Researcher notes

Focus validation on NSCodec SURFACE_BITS_COMMAND handling and whether width and height are bounded against desktop dimensions before decode and copy operations. The commit and advisory are the primary technical anchors. Do not assume exploitability beyond the documented heap overwrite potential without further evidence.

Mitigation direction

  • Upgrade FreeRDP to 3.24.0 or later where directly managed.
  • Apply vendor fixed packages from Red Hat or other distribution advisories.
  • Avoid connecting vulnerable FreeRDP clients to untrusted RDP servers.
  • Prioritize systems used for administrative or privileged remote access.
  • Track vendor guidance for any additional hardening or backported fixes.

Validation and detection

  • Inventory installed FreeRDP package and library versions across endpoints and servers.
  • Confirm direct builds report FreeRDP 3.24.0 or later.
  • Confirm distribution packages map to the relevant vendor fixed advisory.
  • Review remote-access tooling for bundled or statically linked FreeRDP copies.
  • Monitor CVE, GitHub advisory, and vendor errata for status changes.
Prepared
Confidence
high
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-122: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-131: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-31806 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.3 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
20Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.3CVSS 4.0CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——GitHub_M
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

9.3Critical
CVSS 4.0 vector shape for CVE-2026-31806Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPfreerdp: FreeRDP: Arbitrary code execution via crafted Remote Desktop Protocol (RDP) server messages
other:Red Hat severity ratingcvssV3_1
  • 2026-03-13T18:02:52.800Z: Reported to Red Hat.
  • 2026-03-13T17:40:19.920Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
FreeRDPFreeRDP< 3.24.0Listed
Weakness

CWE details

CWE-122CWE-131

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.