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CVE Record

CVE-2026-44420: FreeRDP cliprdr server heap-buffer-overflow via undersized capabilitySetLength in CB_CLIP_CAPS

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.26.0, a malicious RDP client can trigger a heap-buffer-overflow write in FreeRDP's server-side clipboard (cliprdr) channel by sending a CB_CLIP_CAPS PDU with a too-small capabilitySetLength. This can crash the server process (remote DoS) and may be exploitable for code execution because it corrupts heap memory. This vulnerability is fixed in 3.26.0.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A malicious authenticated RDP client can crash a vulnerable FreeRDP server through the clipboard channel. Because the bug writes past a heap buffer, the impact may extend beyond denial of service to code execution. FreeRDP versions before 3.26.0 are affected, and 3.26.0 is listed as the fix.

Executive priority

Treat as high priority for FreeRDP server deployments. The business risk is service disruption and possible compromise of the server process, but the bundle does not confirm active exploitation.

Technical view

CVE-2026-44420 is a server-side FreeRDP cliprdr heap-buffer-overflow write triggered by a CB_CLIP_CAPS PDU with an undersized capabilitySetLength. The source assigns CVSS 3.1 score 8.8, AV:N/AC:L/PR:L/UI:N, with high confidentiality, integrity, and availability impact. CWE-122 and CWE-131 apply.

Likely exposure

Exposure is most likely where FreeRDP server functionality before 3.26.0 accepts RDP client connections and has the clipboard channel enabled or available.

Exploitation context

The provided bundle does not show CISA KEV listing or confirmed active exploitation. The advisory describes a malicious RDP client trigger, requiring low privileges but no user interaction after connection.

Researcher notes

The attack surface is authenticated RDP client interaction with the server-side cliprdr channel. One supplied cpp-httplib advisory appears unrelated to this FreeRDP issue and was not relied on for exploit status or remediation conclusions.

Mitigation direction

  • Upgrade FreeRDP to 3.26.0 or later.
  • Apply applicable vendor packages, including Red Hat advisories where relevant.
  • Restrict RDP server access to trusted clients and networks.
  • Check vendor guidance for supported clipboard-channel mitigations.
  • Prioritize internet-accessible or partner-accessible RDP services.

Validation and detection

  • Inventory FreeRDP installations and record package versions.
  • Confirm vulnerable systems are not running versions earlier than 3.26.0.
  • Identify deployments using FreeRDP server-side clipboard support.
  • Review vendor advisory status for each operating system distribution.
  • Check logs for suspicious RDP client activity or unexplained server crashes.
Prepared
Confidence
high
Sources
7

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.

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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.

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description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2026-44420 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
High
CVSS
8.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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
7Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: noTechnical 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
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9GitHub_M
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

8.8High
CVSS 3.1 vector shape for CVE-2026-44420Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
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 and denial of service via heap-buffer-overflow
other:Red Hat severity ratingcvssV3_1
  • 2026-05-29T21:01:57.327Z: Reported to Red Hat.
  • 2026-05-29T19:42:23.460Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
FreeRDPFreeRDP< 3.26.0Listed
Weakness

CWE details

CWE-122CWE-131

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