CVE-2026-54999 — Windows TCP/IP Remote Code Execution Vulnerability

Executive Summary

Concurrent execution using shared resource with improper synchronization ('race condition') in Windows TCP/IP allows an unauthorized attacker to execute code over an adjacent network.

Overview

8.8

CVSS HIGH

Critical

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Remote Code Execution

Weakness CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Released Jul 14 2026

Last Updated Jul 14 2026

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.00291 — 0.21547 percentile

NVD CVSS 8.8 HIGH — matches MSRC

CVSS Vector

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

ATTACK VECTOR

Adjacent_network

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: 7.7

EPSS Score

0.00291

probability of exploitation in the next 30 days

0.21547 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

27 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 2012	`5099445 (Monthly Rollup)`	Critical	Remote Code Execution	Yes
Windows Server 2012 (Server Core installation)	`5099445 (Monthly Rollup)`	Critical	Remote Code Execution	Yes
Windows Server 2012 R2	`5099444 (Monthly Rollup)`	Critical	Remote Code Execution	Yes
Windows Server 2012 R2 (Server Core installation)	`5099444 (Monthly Rollup)`	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

9 patches

Article	Type	Restart
`5099535`	Security Update	Yes
`5099538`	Security Update	Yes
`5099539`	Security Update	Yes
`5101650`	Security Update	Yes
`5101649`	Security Update	Yes
`5099445`	Monthly Rollup	Yes
`5099444`	Monthly Rollup	Yes
`5099540`	Security Update	Yes
`5099536`	Security Update	Yes

Patch Diff

ghidriff · tcpip.sys (KB5101649)

Race condition (CWE-362) in the Windows TCP/IP driver tcpip.sys wake-port-entry teardown, unauthenticated remote code execution over an adjacent network (Critical, AV:A, CVSS 8.8). tcpip.sys maintains a list of wake port entries (network-wake / low-power port registration); InetWakeAcquirePortAf acquires/creates an entry under a spin lock and entries are removed/freed during teardown. PRE: the teardown performed its list-consistency check and then unlinked and freed the entry (ExFreePoolWithTag) OUTSIDE the protecting lock, so two paths could operate on the same entry concurrently - freeing it while still referenced or freeing it twice. Because the wake port-registration path is reachable via attacker-supplied adjacent-network traffic without authentication, the freed-object reuse is an RCE primitive (Critical 8.8). Diff of tcpip.sys 10.0.28000.2113 (KB5089548) -> .2525 (KB5101649, Jul 14 2026, 26H1) confirms the fix: gated behind CFR flag Feature_2930222395, InetWakeAcquirePortAf now maintains an in-flight word at entry +0x14 under the lock and moves the removal into the new idempotent helper InetWakeRemovePortEntryIfPresent (no PRE counterpart); the unlink becomes idempotent and the free is conditional on the in-flight state so only one side performs the final release. Note: the July tcpip.sys update is very large (55 code changes / 171 modified); most is unrelated churn (e.g. a Feature_TCPIP_Stack_Var_To_Heap_* pool refactor around UdpConnectRedirect) - the isolable fix for this CVE is the wake-port-entry teardown under Feature_2930222395. Stated at confirmed-changed level.

Pre-patch version 10.0.28000.2113 Download

Post-patch version 10.0.28000.2525 Download

Function	Address	Change	Note
`InetWakeAcquirePortAf`	`code change`	code (wake-port-entry teardown made race-safe, CFR-gated)	Pre: list-consistency check then unlink + ExFreePoolWithTag outside the lock (double-free / free-while-in-use). Post (Feature_2930222395): maintains an in-flight word at entry +0x14 under the lock and calls the new idempotent InetWakeRemovePortEntryIfPresent; free conditional on in-flight state so only one side does the final release.
`InetWakeRemovePortEntryIfPresent (added)`	`code change`	added (idempotent port-entry removal)	New helper with no pre-patch counterpart; makes the wake-port-entry unlink idempotent so a concurrent teardown cannot double-free the entry.
`Feature_2930222395`	`gate`	added (CFR gate)	CFR flag gating the race-safe wake-port-entry teardown; the original unsynchronized free ships when disabled. (Distinct from the Feature_TCPIP_Stack_Var_To_Heap_* pool refactor elsewhere in the same update, which is not this CVE.)

View full diff report View RCA report

Attack Path

A race between wake-port-entry teardown and use frees the entry while still referenced

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

Owen McCullough with MSRC V&M

References

MSRC Advisory MITRE NVD