CVE-2026-50655 — Microsoft Windows Media Foundation Remote Code Execution Vulnerability

Executive Summary

Heap-based buffer overflow in Windows Media allows an unauthorized attacker to execute code locally.

Overview

7.8

CVSS HIGH

Critical

MS Severity

Not Exploited

MS Exploit Status

More Likely

MS Exploit Likelihood

Category Remote Code Execution

Weakness CWE-122: Heap-based Buffer Overflow

Released Jul 14 2026

Last Updated Jul 14 2026

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.00505 — 0.40727 percentile

NVD CVSS 7.8 HIGH — matches MSRC

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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

Required

SCOPE

Unchanged

CONFIDENTIALITY

High

INTEGRITY

High

AVAILABILITY

High

EXPLOIT CODE MATURITY

Unproven

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 6.8

EPSS Score

0.00505

probability of exploitation in the next 30 days

0.40727 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

23 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 Version 1607 for 32-bit Systems	`5099535 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 1607 for x64-based Systems	`5099535 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 1809 for 32-bit Systems	`5099538 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 1809 for x64-based Systems	`5099538 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 21H2 for 32-bit Systems	`5099539 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 21H2 for ARM64-based Systems	`5099539 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 21H2 for x64-based Systems	`5099539 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 22H2 for 32-bit Systems	`5099539 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 22H2 for ARM64-based Systems	`5099539 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 10 Version 22H2 for x64-based Systems	`5099539 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 11 Version 24H2 for ARM64-based Systems	`5101650 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 11 Version 24H2 for x64-based Systems	`5101650 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 11 Version 25H2 for ARM64-based Systems	`5101650 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 11 Version 25H2 for x64-based Systems	`5101650 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 11 Version 26H1 for ARM64-based Systems	`5101649 (Security Update)`	Critical	Remote Code Execution	Yes
Windows 11 version 26H1 for x64-based Systems	`5101649 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2016	`5099535 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2016 (Server Core installation)	`5099535 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2019	`5099538 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2019 (Server Core installation)	`5099538 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2022	`5099540 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2025	`5099536 (Security Update)`	Critical	Remote Code Execution	Yes
Windows Server 2025 (Server Core installation)	`5099536 (Security Update)`	Critical	Remote Code Execution	Yes

Patches

7 patches

Article	Type	Restart
`5099535`	Security Update	Yes
`5099538`	Security Update	Yes
`5099539`	Security Update	Yes
`5101650`	Security Update	Yes
`5101649`	Security Update	Yes
`5099540`	Security Update	Yes
`5099536`	Security Update	Yes

Patch Diff

ghidriff · mfaudiocnv.dll (KB5099535)

Integer overflow leading to a heap-based buffer overflow (CWE-122) in the Windows Media Foundation audio converter mfaudiocnv.dll (DTS audio MFT, CDTSMFTDataHandler), local arbitrary code execution when a user opens a crafted media file (Critical, RCE, AV:L, UI:R, CVSS 7.8, Exploitation More Likely). When producing output samples, _CreateNewOutputBuffer and _AppendPacketToOutputBuffer compute the required output-buffer size by adding a fixed header size to the payload length (payload + 8, payload + 4, payload + 0x13 aligned) and compare it against the buffer capacity. PRE: the size was computed in 32-bit and compared (unsigned) to capacity with no overflow check, so a crafted stream whose payload length is near 0xFFFFFFFF wraps the addition to a small value that passes the capacity check while the real copy overruns the buffer. Because a user need only open/play a crafted audio file, it is an ACE primitive. Diff of mfaudiocnv.dll 10.0.14393.4169 -> .9339 (Jul 14 2026, KB5099535, Server 2016) confirms the fix: gated via the velocity EvaluateCurrentState mechanism (Feature_2888010040 in _CreateNewOutputBuffer, Feature_3712716091 in _AppendPacketToOutputBuffer), each header+payload addition gains a monotonicity check - if (payload + 8 < payload) the 32-bit add wrapped, so it rejects with 0x8000FFFF (E_UNEXPECTED) before the size drives the capacity comparison/copy; the same guard is applied to the payload+4 and payload+0x13+hdr calculations. Cross-checked against an independent writeup (the size-addition sites and the monotonicity fix match; the writeup cites Feature_2552465720 while this build shows Feature_2888010040 / Feature_3712716091, and the capacity-field offset differs because the object layout changed between the two revisions).

Pre-patch version 10.0.14393.4169 Download

Post-patch version 10.0.14393.9339 Download

Function	Address	Change	Note
`CDTSMFTDataHandler::_CreateNewOutputBuffer`	`code change`	code (adds 32-bit overflow/monotonicity guard on the size addition, CFR-gated)	Pre: uVar8 = (payload + 0x13) & ~0xF then wrote size (short)uVar8 + 8 with no overflow check. Post (Feature_2888010040): uVar3 = payload + 8; if (uVar3 < payload) set 0x8000FFFF (E_UNEXPECTED) before using the size / comparing to capacity.
`CDTSMFTDataHandler::_AppendPacketToOutputBuffer`	`code change`	code (guarded header+payload additions vs capacity, CFR-gated)	Post (Feature_3712716091): computes payload + 0x13 + hdr (aligned) and payload + 8 + hdr and checks them against capacity (local_res8[0]) with the wrap guard, rejecting with 0x8000FFFF when the 32-bit add would overflow.
`Feature_2888010040 / Feature_3712716091`	`gate`	added (CFR gates, velocity EvaluateCurrentState)	Feature descriptors gating the overflow guards in the two sizing functions; the original unchecked additions ship when disabled. (An independent writeup cites Feature_2552465720 for the same fix.)

View full diff report View RCA report

Attack Path

A crafted audio payload length overflows the 32-bit output-buffer size computation, bypassing the capacity check

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.

Exploits & PoC

No public exploit or PoC has been linked for this CVE yet. When available, references are sourced from public repositories and may be unverified or non-functional — review carefully before use.

Detection Rules

No public Sigma or Nuclei detection rule has been mapped to this CVE yet. Coverage is concentrated on exploited / high-profile vulnerabilities; check SigmaHQ for updates.

Acknowledgments

Kyeongmin Kim (@hareh4ru)

References

MSRC Advisory MITRE NVD