PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-55827 FreeRDP CVE debrief

CVE-2026-55827 is a heap out-of-bounds write vulnerability in FreeRDP, a free implementation of the Remote Desktop Protocol. This issue allows a malicious RDP server to trigger a heap out-of-bounds write with attacker-controlled offset and content when FreeRDP clients are launched with the non-default /cache:codec:rfx option. Affected product deployments should be identified, and owners assigned for follow-up. Official advisories should be reviewed to validate affected scope, severity, and vendor guidance.

Vendor
FreeRDP
Product
Unknown
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-10
Original CVE updated
2026-07-13
Advisory published
2026-07-10
Advisory updated
2026-07-13

Who should care

Users of FreeRDP clients, especially those using versions prior to 3.27.1, should be aware of this vulnerability and take steps to mitigate it. Affected operators, platforms, vulnerability-management, and security teams should review the vulnerability and implement necessary security measures.

Technical summary

Prior to version 3.27.1, FreeRDP clients launched with the non-default /cache:codec:rfx option pass desktop stride and height to RemoteFX decoding for Cache Bitmap V3 data while allocating bitmap->data only for the smaller DstWidth and DstHeight in gdi_Bitmap_Decompress. This allows a malicious RDP server to trigger a heap out-of-bounds write with attacker-controlled offset and content. Defenders should review compensating controls for exposed systems while remediation is scheduled and verified.

Defensive priority

High

Recommended defensive actions

  • Update FreeRDP to version 3.27.1 or later
  • Avoid using the /cache:codec:rfx option unless necessary
  • Monitor for suspicious RDP activity
  • Implement additional security measures such as network segmentation and access controls
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record was published on 2026-07-10T20:16:48.060Z and has not been modified since then. The NVD entry is currently being reviewed. Evidence limits suggest that FreeRDP clients launched with the non-default /cache:codec:rfx option are vulnerable to a heap out-of-bounds write. Defenders should verify affected product deployments and review official advisories for scope, severity, and vendor guidance.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-55827 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-55827

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

  • CVE-2026-55827 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-55827

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

Supplemental references

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.