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Microsoft Streaming Service

CVE-2023-29360 — Microsoft Streaming Service Elevation of Privilege Vulnerability

Important CVSS 8.4 EPSS 0.22133 🔬 Patch diffed 2023-06 archive

Executive Summary

None

Overview

8.4
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
More Likely
MS Exploit Likelihood
Category Elevation of Privilege
Weakness CWE-822: Untrusted Pointer Dereference
Released Jun 13 2023
Last Updated Jun 13 2023
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.22133 — 0.97458 percentile
NVD CVSS 8.4 HIGH — matches MSRC

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
ATTACK VECTOR
Local
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
None
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
High
INTEGRITY
High
AVAILABILITY
High
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 7.3

EPSS Score

0.22133
probability of exploitation in the next 30 days
0.97458 percentile - updated 2026-08-14
View on FIRST.org

Affected Products

19 affected products
Product KB Article Severity Impact Restart Required
Windows 10 Version 1607 for 32-bit Systems 5027219 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 1607 for x64-based Systems 5027219 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 1809 for 32-bit Systems 5027222 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 1809 for ARM64-based Systems 5027222 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 1809 for x64-based Systems 5027222 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for 32-bit Systems 5027215 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for ARM64-based Systems 5027215 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for x64-based Systems 5027215 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for 32-bit Systems 5027215 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for ARM64-based Systems 5027215 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for x64-based Systems 5027215 (Security Update) Important Elevation of Privilege Yes
Windows 11 version 21H2 for ARM64-based Systems 5027223 (Security Update) Important Elevation of Privilege Yes
Windows 11 version 21H2 for x64-based Systems 5027223 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 22H2 for ARM64-based Systems 5027231 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 22H2 for x64-based Systems 5027231 (Security Update) Important Elevation of Privilege Yes
Windows Server 2016 5027219 (Security Update) Important Elevation of Privilege Yes
Windows Server 2016 (Server Core installation) 5027219 (Security Update) Important Elevation of Privilege Yes
Windows Server 2019 5027222 (Security Update) Important Elevation of Privilege Yes
Windows Server 2019 (Server Core installation) 5027222 (Security Update) Important Elevation of Privilege Yes

Patches

5 patches
Article Type Restart
5027219 Security Update Yes
5027222 Security Update Yes
5027215 Security Update Yes
5027223 Security Update Yes
5027231 Security Update Yes

Patch Diff

ghidriff · mskssrv.sys (KB5027231)

Patch diff 10.0.22621.1 -> 10.0.22621.1848 (single-function fix: FsAllocAndLockMdl MmProbeAndLockPages PreviousMode)

Pre-patch version 10.0.22621.1
Post-patch version 10.0.22621.1848
Function Address Change Note
FsAllocAndLockMdl 1c0001650 code, length, sig similarity 0.9
View full diff report View RCA report Download PoC

Attack Path

Local EoP via an MDL built over a user address but probed as KernelMode in mskssrv.sys

Attack path for CVE-2023-29360 Local EoP via an MDL built over a user address but probed as KernelMode in mskssrv.sys 01 — ENTRY Attacker opens the streaming service device and issues the publish IOCTL DeviceIoControl(hDevice, 0x2F0408). mskssrv.sys is present on all Windows 10/11 systems and the camera/streaming interface is reachable without elevation. 02 — CONTROLLED INPUT Supplies the buffer address and size that the MDL will be built over FSFrameMdl::AllocateMdl copies the user request and passes the attacker-chosen address and length straight into the allocation helper. 03 — PATH The publish path descends into MDL allocation and page locking SrvDispatchIoControl -> FSRendezvousServer::PublishTx -> FSStreamReg::PublishTx -> FSFrameMdl::AllocateMdl -> FsAllocAndLockMdl. 04 — MISSING CHECK MmProbeAndLockPages is called with KernelMode on a user-supplied address IoAllocateMdl(user_addr, user_size) followed by MmProbeAndLockPages(mdl, KernelMode, IoWriteAccess). KernelMode skips the user-space range check entirely, so a kernel address passes validation. The patch probes as UserMode. 05 — PRIMITIVE Kernel memory locked and written through as if it were the caller's buffer Any kernel address can be mapped writable into the request, giving a controlled kernel write and a path to SYSTEM.

Derived from the patch delta: the checks added by the vendor identify which fields crossed a trust boundary unvalidated. Reachability and privilege are taken from the call chain in the RCA report.

Known Exploits

Acknowledgments

Thomas Imbert (@masthoon) from Synacktiv (@Synacktiv) Working with Trend Micro Zero Day Initiative

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