CVE-2026-23534Network attack vector

Client crash via off-by-one ClearCodec bounds checks

Published Jan 19, 2026 · Updated Jan 19, 2026

Heap buffer overflow in FreeRDP before 3.21.0 allows remote attackers operating an RDP server to crash a connecting client. In clear_decompress_bands_data, inclusive upper-bound checks accept stream-supplied band coordinates equal to the surface dimensions, so FreeRDPWriteColor_int writes beyond the destination surface buffer. The client must process a crafted WIRE_TO_SURFACE_PDU_1 from the server; the demonstrated consequence is a crash, while resulting heap corruption creates allocator- and layout-dependent code-execution risk.

CVSS severity9.8
Critical
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in FreeRDP before 3.21.0 allows remote attackers operating an RDP server to crash a connecting client. In clear_decompress_bands_data, inclusive upper-bound checks accept stream-supplied band coordinates equal to the surface dimensions, so FreeRDPWriteColor_int writes beyond the destination surface buffer. The client must process a crafted WIRE_TO_SURFACE_PDU_1 from the server; the demonstrated consequence is a crash, while resulting heap corruption creates allocator- and layout-dependent code-execution risk.

The record

CVE
CVE-2026-23534
Published
Jan 19, 2026
Updated
Jan 19, 2026
Vendor
FreeRDP
Product
FreeRDP
Classifications
CWE-122, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.21.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FreeRDP · FreeRDPversion=< 3.21.0

Published CVSS scores

7.6redhat-SADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.7GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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