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CVE Record

CVE-2026-33983: FreeRDP: Progressive Codec Quant BYTE Underflow - UB + CPU DoS

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.24.2, progressive_decompress_tile_upgrade() detects a mismatch via progressive_rfx_quant_cmp_equal() but only emits WLog_WARN, execution continues. The wrapped value (247) is used as a shift exponent, causing undefined behavior and an approximately 80 billion iteration loop (CPU DoS). 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

CVE-2026-33983 can let a remote party make vulnerable FreeRDP versions consume excessive CPU, causing denial of service. The issue is fixed in FreeRDP 3.24.2. The business risk is service disruption where FreeRDP is used in remote desktop workflows, automation, jump hosts, containers, or packaged desktop clients.

Executive priority

Treat as a high-priority availability fix, especially for remote access operations. It is not described as a breach-enabling flaw, but it can disrupt users or automation that depend on FreeRDP.

Technical view

Before FreeRDP 3.24.2, progressive_decompress_tile_upgrade() logged a quantization mismatch but continued processing. A wrapped byte value could become a large shift exponent, causing undefined behavior and an approximately 80 billion iteration loop. The CVSS 3.1 vector is AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Likely exposure

Exposure is limited to environments running FreeRDP versions before 3.24.2, including downstream packages. Risk is highest where FreeRDP processes RDP data from untrusted or externally reachable sources.

Exploitation context

The provided bundle does not show CISA KEV listing or cited evidence of active exploitation. The advisory describes a remotely reachable, unauthenticated denial-of-service condition, but not data theft, code execution, or integrity impact.

Researcher notes

Key weakness pattern is integer underflow plus unchecked error handling: mismatch detection emitted only a warning and execution continued. Focus validation on vulnerable progressive codec paths and downstream package status, without assuming exploit activity from the provided evidence.

Mitigation direction

  • Upgrade FreeRDP to version 3.24.2 or later.
  • Apply applicable Red Hat RHSA updates for packaged FreeRDP deployments.
  • Check distro vendor guidance for backported fixed package versions.
  • Reduce vulnerable FreeRDP use against untrusted RDP endpoints until patched.

Validation and detection

  • Inventory FreeRDP versions across hosts, containers, and desktop images.
  • Confirm installed packages include the 3.24.2 fix or vendor backport.
  • Map affected systems to exposed RDP workflows and automation jobs.
  • Monitor vulnerable systems for abnormal FreeRDP CPU exhaustion events.
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-190: 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-252: 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-2026-33983 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:L/PR:N/UI:N/S:U/C:N/I:N/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: partial

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:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP
6.5CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H2.83.6GitHub_M

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-33983Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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: Denial of Service via specially crafted Remote Desktop Protocol messages
other:Red Hat severity ratingcvssV3_1
  • 2026-03-30T22:01:29.031Z: Reported to Red Hat.
  • 2026-03-30T21:42:27.798Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
FreeRDPFreeRDP< 3.24.2Listed
Weakness

CWE details

CWE-190CWE-252

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