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PatchSiren cyber security CVE debrief

CVE-2026-23884 FreeRDP CVE debrief

CVE-2026-23884 is a high-severity vulnerability in FreeRDP, a free implementation of the Remote Desktop Protocol. The vulnerability, caused by offscreen bitmap deletion leaving `gdi->drawing` pointing to freed memory, can lead to a use-after-free (UAF) condition when related update packets arrive. This can cause a crash (DoS) and potentially lead to heap corruption with code-execution risk, depending on allocator behavior and surrounding heap layout. A malicious server can trigger this vulnerability on the client-side. Version 3.21.0 of FreeRDP contains a patch for the issue. Users of affected versions should update to version 3.21.0 or later to mitigate this vulnerability.

Vendor
FreeRDP
Product
Unknown
CVSS
HIGH 7.7
CISA KEV
Not listed in stored evidence
Original CVE published
2026-01-19
Original CVE updated
2026-07-15
Advisory published
2026-01-19
Advisory updated
2026-07-15

Who should care

Organizations and individuals using FreeRDP versions prior to 3.21.0 should be aware of this vulnerability and take steps to mitigate it. This includes updating to version 3.21.0 or later, and ensuring that all clients and servers are patched. Additionally, defenders should monitor for potential exploitation attempts and be prepared to respond to incidents.

Technical summary

The vulnerability is caused by offscreen bitmap deletion leaving `gdi->drawing` pointing to freed memory. When related update packets arrive, this can lead to a use-after-free (UAF) condition. The vulnerability has a CVSS score of 7.7 and is classified as HIGH severity. The vulnerability can be triggered by a malicious server on the client-side, and can cause a crash (DoS) and potentially lead to heap corruption with code-execution risk.

Defensive priority

High priority should be given to patching affected systems, as the vulnerability can be triggered remotely and has a high severity score. Defenders should also monitor for potential exploitation attempts and be prepared to respond to incidents.

Recommended defensive actions

  • Update to version 3.21.0 or later of FreeRDP
  • Ensure all clients and servers are patched
  • Monitor for potential exploitation attempts
  • Be prepared to respond to incidents
  • Review and update incident response plans

Evidence notes

The vulnerability was reported by an unknown source and patched in version 3.21.0 of FreeRDP. The CVE record and NVD detail provide additional information on the vulnerability. Red Hat has also provided errata for affected systems.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-23884 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-23884

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-23884 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-23884

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://github.com/FreeRDP/FreeRDP/blob/3370e30e92a021eb680892dda14d642bc8b8727c/libfreerdp/cache/offscreen.c

    [email protected] - Product

  • Source reference

    Unverified legacy reference

    URL: https://github.com/FreeRDP/FreeRDP/blob/3370e30e92a021eb680892dda14d642bc8b8727c/libfreerdp/cache/offscreen.c

    [email protected] - Product

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://github.com/FreeRDP/FreeRDP/releases/tag/3.21.0

    [email protected] - Release Notes

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-cfgj-vc84-f3pp

    [email protected] - Exploit, Vendor Advisory

  • Source reference

    Unverified legacy reference

    URL: https://access.redhat.com/errata/RHSA-2026:2048

    0b0ca135-0b70-47e7-9f44-1890c2a1c46c

  • Source reference

    Unverified legacy reference

    URL: https://access.redhat.com/errata/RHSA-2026:2081

    0b0ca135-0b70-47e7-9f44-1890c2a1c46c

  • Source reference

    Unverified legacy reference

    URL: https://access.redhat.com/errata/RHSA-2026:2222

    0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.