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CVE Record

CVE-2026-23534: FreeRDP has heap-buffer-overflow in clear_decompress_bands_data

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.21.0, a client-side heap buffer overflow occurs in the ClearCodec bands decode path when crafted band coordinates allow writes past the end of the destination surface buffer. A malicious server can trigger a client‑side heap buffer overflow, causing a crash (DoS) and potential heap corruption with code‑execution risk depending on allocator behavior and surrounding heap layout. Version 3.21.0 contains a patch for the issue.

HighCVSS 7.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

FreeRDP clients before 3.21.0 can be crashed by a malicious RDP server through malformed ClearCodec graphics data. The sources also describe possible heap corruption and code-execution risk, but do not confirm real-world exploitation. Organizations using FreeRDP should prioritize updating clients and downstream packages.

Executive priority

Treat as high priority for desktop, jump-host, support, and automation environments using FreeRDP. The main confirmed risk is client crash, with credible memory-corruption risk. Patch promptly, but do not assume active exploitation from the provided evidence.

Technical view

The flaw is a CWE-122 heap buffer overflow in clear_decompress_bands_data. Crafted band coordinates in the ClearCodec bands decode path can write past the destination surface buffer. The documented impact is client-side DoS with potential heap corruption; FreeRDP 3.21.0 contains the patch.

Likely exposure

Exposure is most likely where FreeRDP client libraries or command-line clients below 3.21.0 connect to malicious, compromised, or untrusted RDP servers. Downstream Linux packages should be checked against vendor advisories such as Red Hat errata.

Exploitation context

The provided bundle says KEV is false and does not cite active exploitation. The attacker position is a malicious server sending crafted graphics data to a vulnerable FreeRDP client. No exploit steps or public weaponization evidence are provided in the sources.

Researcher notes

The evidence identifies the affected function, vulnerable decode path, bug class, and fixed release. The bundle does not provide exploitability proof beyond potential heap corruption, nor does it establish exploitation in the wild. Validate exposure through version and package lineage, not product-name matching alone.

Mitigation direction

  • Upgrade FreeRDP to version 3.21.0 or later.
  • Apply relevant downstream vendor security updates, including Red Hat errata where applicable.
  • Limit FreeRDP client connections to trusted RDP servers until patched.
  • Check vendor guidance for packaged or embedded FreeRDP copies.

Validation and detection

  • Inventory systems for FreeRDP clients and libraries.
  • Confirm installed FreeRDP versions are 3.21.0 or later.
  • Review Red Hat CSAF/VEX and errata for package-specific status.
  • Verify vulnerable clients cannot connect broadly to untrusted RDP servers.
Prepared
Confidence
high
Sources
11

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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cve · low confidence lookup

CVE-2026-23534 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
7.7 (4.0)
Known Exploited
No
Published

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

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
13Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical 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
7.7CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P——GitHub_M
7.6CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H2.84.7redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

7.7High
CVSS 4.0 vector shape for CVE-2026-23534Attack 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:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P

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 and denial of service via client-side heap buffer overflow
other:Red Hat severity ratingcvssV3_1
  • 2026-01-19T18:01:57.575Z: Reported to Red Hat.
  • 2026-01-19T17:09:55.715Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
FreeRDPFreeRDP< 3.21.0Listed
Weakness

CWE details

CWE-122

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.

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