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TI-2026-21441 Aliases CVE-2026-26955

FreeRDP has Out-of-bounds Write

Priority HIGH 73CWE-787Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-787 and the CVSS impact.

Summary

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.23.0, a malicious RDP server can trigger a heap buffer overflow in FreeRDP clients using the GDI surface pipeline (e.g., `xfreerdp`) by sending an RDPGFX ClearCodec surface command with an out-of-bounds destination rectangle. The `gdi_SurfaceCommand_ClearCodec()` handler does not call `is_within_surface()` to validate the command rectangle against the destination surface dimensions, allowing attacker-controlled `cmd->left`/`cmd->top` (and subcodec rectangle offsets) to reach image copy routines that write into `surface->data` without bounds enforcement. The OOB write corrupts an adjacent `gdiGfxSurface` struct's `codecs*` pointer with attacker-controlled pixel data, and corruption of `codecs*` is sufficient to reach an indirect function pointer call (`NSC_CONTEXT.decode` at `nsc.c:500`) on a subsequent codec command — full instruction pointer (RIP) control demonstrated in exploitability harness. Users should upgrade to version 3.23.0 to receive a patch.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00645 51st percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed FreeRDP (FreeRDP): 3.23.0Red Hat: 14 advisories

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
FreeRDPFreeRDPbefore 3.23.03.23.0Patch availableCNA
  • FreeRDP VendorFreeRDP Affected before 3.23.0 Fixed in 3.23.0 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:freerdp:freerdp:*:*:*:*:*:*:*:*before 3.23.0VulnerableFreeRDP
  • cpe:2.3:a:freerdp:freerdp:*:*:*:*:*:*:*:* Versions before 3.23.0 Vulnerable ·FreeRDP

Remediation

  • Fix · CNA FreeRDP (FreeRDP) Fixed in 3.23.0

Red Hat 14 advisories

  • RHSA-2026:19033 Released 2026-05-19 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream (v. 10) freerdp-2:3.10.3-12.el10_2.2, freerdp-libs-2:3.10.3-12.el10_2.2, libwinpr-2:3.10.3-12.el10_2.2
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) freerdp-devel-2:3.10.3-12.el10_2.2, freerdp-server-2:3.10.3-12.el10_2.2, libwinpr-devel-2:3.10.3-12.el10_2.2
  • RHSA-2026:7292 Released 2026-04-09 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux Server (v. 7 ELS) freerdp-2.1.1-5.el7_9.5, freerdp-libs-2.1.1-5.el7_9.5, freerdp-libs-2.1.1-5.el7_9.5.ppc +2
    • Red Hat Enterprise Linux Server Optional (v. 7 ELS) freerdp-devel-2.1.1-5.el7_9.5, freerdp-devel-2.1.1-5.el7_9.5.ppc, libwinpr-devel-2.1.1-5.el7_9.5 +1
  • RHSA-2026:6764 Released 2026-04-07 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream E4S (v.8.8) freerdp-2:2.2.0-12.el8_8.3, freerdp-libs-2:2.2.0-12.el8_8.3, libwinpr-2:2.2.0-12.el8_8.3 +1
    • Red Hat Enterprise Linux AppStream TUS (v.8.8) freerdp-2:2.2.0-12.el8_8.3, freerdp-libs-2:2.2.0-12.el8_8.3, libwinpr-2:2.2.0-12.el8_8.3 +1
Show 11 more Red Hat advisories
  • RHSA-2026:6712 Released 2026-04-06 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream AUS (v. 8.2) freerdp-2:2.0.0-46.rc4.el8_2.8, freerdp-libs-2:2.0.0-46.rc4.el8_2.8, libwinpr-2:2.0.0-46.rc4.el8_2.8 +1
  • RHSA-2026:6665 Released 2026-04-06 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.6) freerdp-2:2.2.0-7.el8_6.3, freerdp-libs-2:2.2.0-7.el8_6.3, libwinpr-2:2.2.0-7.el8_6.3 +1
    • Red Hat Enterprise Linux AppStream E4S (v.8.6) freerdp-2:2.2.0-7.el8_6.3, freerdp-libs-2:2.2.0-7.el8_6.3, libwinpr-2:2.2.0-7.el8_6.3 +1
    • Red Hat Enterprise Linux AppStream TUS (v.8.6) freerdp-2:2.2.0-7.el8_6.3, freerdp-libs-2:2.2.0-7.el8_6.3, libwinpr-2:2.2.0-7.el8_6.3 +1
  • RHSA-2026:6616 Released 2026-04-06 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.4) freerdp-2:2.2.0-10.el8_4, freerdp-libs-2:2.2.0-10.el8_4, libwinpr-2:2.2.0-10.el8_4 +1
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) freerdp-2:2.2.0-10.el8_4, freerdp-libs-2:2.2.0-10.el8_4, libwinpr-2:2.2.0-10.el8_4 +1
  • RHSA-2026:6396 Released 2026-04-01 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.2) freerdp-2:2.4.1-6.el9_2.4, freerdp-libs-2:2.4.1-6.el9_2.4, libwinpr-2:2.4.1-6.el9_2.4
  • RHSA-2026:6395 Released 2026-04-01 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.0) freerdp-2:2.4.1-3.el9_0.2, freerdp-libs-2:2.4.1-3.el9_0.2, libwinpr-2:2.4.1-3.el9_0.2
  • RHSA-2026:6385 Released 2026-04-01 · Red Hat rating Important
    freerdp security update
    • Red Hat CodeReady Linux Builder EUS (v.9.6) freerdp-devel-2:2.11.7-1.el9_6.5, libwinpr-devel-2:2.11.7-1.el9_6.5
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) freerdp-2:2.11.7-1.el9_6.5, freerdp-libs-2:2.11.7-1.el9_6.5, libwinpr-2:2.11.7-1.el9_6.5
  • RHSA-2026:6384 Released 2026-04-01 · Red Hat rating Important
    freerdp security update
    • Red Hat CodeReady Linux Builder EUS (v.9.4) freerdp-devel-2:2.11.2-1.el9_4.3, libwinpr-devel-2:2.11.2-1.el9_4.3
    • Red Hat Enterprise Linux AppStream EUS (v.9.4) freerdp-2:2.11.2-1.el9_4.3, freerdp-libs-2:2.11.2-1.el9_4.3, libwinpr-2:2.11.2-1.el9_4.3
  • RHSA-2026:6005 Released 2026-03-30 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream (v. 8) freerdp-2:2.11.7-4.el8_10, freerdp-libs-2:2.11.7-4.el8_10, libwinpr-2:2.11.7-4.el8_10 +1
    • Red Hat Enterprise Linux CRB (v. 8) freerdp-devel-2:2.11.7-4.el8_10
  • RHSA-2026:6004 Released 2026-03-30 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream (v. 9) freerdp-2:2.11.7-1.el9_7.3, freerdp-libs-2:2.11.7-1.el9_7.3, libwinpr-2:2.11.7-1.el9_7.3
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) freerdp-devel-2:2.11.7-1.el9_7.3, libwinpr-devel-2:2.11.7-1.el9_7.3
  • RHSA-2026:5939 Released 2026-03-26 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream (v. 10) freerdp-2:3.10.3-5.el10_1.3, freerdp-libs-2:3.10.3-5.el10_1.3, libwinpr-2:3.10.3-5.el10_1.3
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) freerdp-devel-2:3.10.3-5.el10_1.3, freerdp-server-2:3.10.3-5.el10_1.3, libwinpr-devel-2:3.10.3-5.el10_1.3
  • RHSA-2026:5936 Released 2026-03-26 · Red Hat rating Important
    freerdp security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) freerdp-2:3.10.3-3.el10_0.3, freerdp-libs-2:3.10.3-3.el10_0.3, libwinpr-2:3.10.3-3.el10_0.3
    • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) freerdp-devel-2:3.10.3-3.el10_0.3, freerdp-server-2:3.10.3-3.el10_0.3, libwinpr-devel-2:3.10.3-3.el10_0.3

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat CodeReady Linux Builder EUS (v.9.4)Fixed RHSA-2026:6384
Red Hat CodeReady Linux Builder EUS (v.9.6)Fixed RHSA-2026:6385
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:19033, RHSA-2026:5939
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2026:6005
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:6004
Red Hat Enterprise Linux AppStream AUS (v. 8.2)Fixed RHSA-2026:6712
Red Hat Enterprise Linux AppStream AUS (v.8.4)Fixed RHSA-2026:6616
Red Hat Enterprise Linux AppStream AUS (v.8.6)Fixed RHSA-2026:6665
Red Hat Enterprise Linux AppStream E4S (v.8.6)Fixed RHSA-2026:6665
Red Hat Enterprise Linux AppStream E4S (v.8.8)Fixed RHSA-2026:6764
Red Hat Enterprise Linux AppStream E4S (v.9.0)Fixed RHSA-2026:6395
Red Hat Enterprise Linux AppStream E4S (v.9.2)Fixed RHSA-2026:6396
Red Hat Enterprise Linux AppStream EUS (v. 10.0)Fixed RHSA-2026:5936
Red Hat Enterprise Linux AppStream EUS (v.9.4)Fixed RHSA-2026:6384
Red Hat Enterprise Linux AppStream EUS (v.9.6)Fixed RHSA-2026:6385
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)Fixed RHSA-2026:6616
Red Hat Enterprise Linux AppStream TUS (v.8.6)Fixed RHSA-2026:6665
Red Hat Enterprise Linux AppStream TUS (v.8.8)Fixed RHSA-2026:6764
Red Hat Enterprise Linux CRB (v. 8)Fixed RHSA-2026:6005
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)Fixed RHSA-2026:19033, RHSA-2026:5939
Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)Fixed RHSA-2026:6004
Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0)Fixed RHSA-2026:5936
Red Hat Enterprise Linux Server (v. 7 ELS)Fixed RHSA-2026:7292
Red Hat Enterprise Linux Server Optional (v. 7 ELS)Fixed RHSA-2026:7292
Not affected: 1 product
  • Red Hat Enterprise Linux 6

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-26955
  2. 2026-10-23 EPSS moved to the 50th–90th percentile

References

Exploit 1

Patch 1

  • TI-2026-85092 Use-after-free in FreeRDP rdpgfx channel close handling CVSS 4.0CRITICAL 9.3
  • TI-2026-85091 Out-of-bounds write in FreeRDP proxy via bitmap cache v2 capability CVSS 4.0CRITICAL 9.3
  • TI-2026-24435 FreeRDP has a `size_t` underflow in ADPCM decoder leads to heap-buffer-overflow write CVSS 3.1CRITICAL 9.8
  • TI-2023-21373 Out-Of-Bounds Write in FreeRDP CVSS 3.1CRITICAL 9.8
  • TI-2022-08692 Server side NTLM does not properly check parameters in FreeRDP CVSS 3.1CRITICAL 9.1
  • TI-2023-21374 Out-Of-Bounds Read in FreeRDP CVSS 3.1CRITICAL 9.1
See all 336 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences