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CVE Record

CVE-2026-33984: FreeRDP: ClearCodec resize_vbar_entry() Heap OOB Write

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.24.2, in resize_vbar_entry() in libfreerdp/codec/clear.c, vBarEntry->size is updated to vBarEntry->count before the winpr_aligned_recalloc() call. If realloc fails, size is inflated while pixels still points to the old, smaller buffer. On a subsequent call where count <= size (the inflated value), realloc is skipped. The caller then writes count * bpp bytes of attacker-controlled pixel data into the undersized buffer, causing a heap buffer overflow. This issue has been patched in version 3.24.2.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

FreeRDP versions before 3.24.2 can mishandle memory when processing ClearCodec graphics data. A malicious or compromised RDP endpoint could trigger a heap overflow in a user’s FreeRDP client, potentially affecting confidentiality, integrity, and availability. The issue is fixed in FreeRDP 3.24.2.

Executive priority

Prioritize remediation in environments where FreeRDP users connect to external, third-party, or less trusted RDP systems. The issue is high severity with broad impact potential, but current provided evidence does not show active exploitation.

Technical view

In libfreerdp/codec/clear.c, resize_vbar_entry() updates vBarEntry->size before reallocating. If reallocation fails, size can exceed the real buffer. Later calls may skip allocation and copy attacker-controlled pixel data beyond the old heap buffer. CVSS 3.1 is 7.5: AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.

Likely exposure

Exposure is likely where FreeRDP before 3.24.2 is installed, embedded, or packaged, especially clients connecting to untrusted or compromised RDP endpoints. Red Hat has multiple related advisories, so distribution packages may need vendor-specific fixed builds rather than only upstream version checks.

Exploitation context

The provided sources do not show CISA KEV listing or confirmed active exploitation. Exploitation requires user interaction and high complexity, but the impact could be severe because successful memory corruption may affect confidentiality, integrity, and availability.

Researcher notes

Focus review on ClearCodec handling in FreeRDP before 3.24.2 and vendor backports. The core condition is failed reallocation leaving an inflated logical size over a smaller heap buffer. Avoid assuming exploitability beyond the advisory’s high-complexity CVSS context.

Mitigation direction

  • Upgrade FreeRDP to version 3.24.2 or later.
  • Apply applicable Red Hat security errata for affected packages.
  • Inventory applications, containers, and appliances that bundle FreeRDP.
  • Restrict FreeRDP use to trusted RDP servers until patched.
  • Monitor vendor guidance for backported fixed package versions.

Validation and detection

  • Check installed FreeRDP versions and confirm 3.24.2 or vendor-fixed builds.
  • Review SBOMs and container images for bundled FreeRDP libraries.
  • Confirm Red Hat errata applicability for deployed distributions.
  • Verify users cannot reach untrusted RDP endpoints from vulnerable clients.
  • Track remediation evidence in vulnerability management records.
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.

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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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cve · low confidence lookup

CVE-2026-33984 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
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/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
20Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: 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
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H1.65.9GitHub_M
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H1.65.9redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-33984Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/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: Heap buffer overflow allows arbitrary code execution via crafted pixel data
other:Red Hat severity ratingcvssV3_1
  • 2026-03-30T22:01:24.523Z: Reported to Red Hat.
  • 2026-03-30T21:42:57.090Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
FreeRDPFreeRDP< 3.24.2Listed
Weakness

CWE details

CWE-122CWE-131

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

CWE-122 · source CWE mapping

Heap-based Buffer Overflow

Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-131 · source CWE mapping

Incorrect Calculation of Buffer Size

Incorrect Calculation of Buffer Size represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs