CVE-2026-45592 — Windows Internet (wininet.dll) Elevation of Privilege Vulnerability

Executive Summary

Integer overflow or wraparound in Windows Internet (wininet.dll) allows an authorized attacker to elevate privileges locally.

Overview

7.8

CVSS HIGH

Important

MS Severity

Not Exploited

MS Exploit Status

Exploitation Unlikely

MS Exploit Likelihood

Category Elevation of Privilege

Weakness CWE-190: Integer Overflow or Wraparound

Released Jun 9 2026

Last Updated Jun 9 2026

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.00286 — 0.21027 percentile

NVD CVSS 7.8 HIGH — matches MSRC

CVSS Vector

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

ATTACK VECTOR

Local

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

Low

USER INTERACTION

None

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

0.00286

probability of exploitation in the next 30 days

0.21027 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

26 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 Version 1607 for 32-bit Systems	`5094122 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1607 for x64-based Systems	`5094122 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for 32-bit Systems	`5094123 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for x64-based Systems	`5094123 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for 32-bit Systems	`5094127 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for ARM64-based Systems	`5094127 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for x64-based Systems	`5094127 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for 32-bit Systems	`5094127 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for ARM64-based Systems	`5094127 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for x64-based Systems	`5094127 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 23H2 for ARM64-based Systems	`5093998 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 23H2 for x64-based Systems	`5093998 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 24H2 for ARM64-based Systems	`5094126 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 24H2 for x64-based Systems	`5094126 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 25H2 for ARM64-based Systems	`5094126 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 25H2 for x64-based Systems	`5094126 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 26H1 for ARM64-based Systems	`5095051 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 version 26H1 for x64-based Systems	`5095051 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2012 R2 5094041 (Monthly Rollup) 5094006 (IE Cumulative) Important Elevation of Privilege 5087471 5082806 Base: 7.8 Temporal: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.3.9600.23228 1.000 Yes None Windows Server 2012 R2 (Server Core installation) 5094041 (Monthly Rollup) 5094006 (IE Cumulative) Important Elevation of Privilege 5087471 5082806 Base: 7.8 Temporal: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.3.9600.23228 1.000 Yes None Windows Server 2016	`5094122 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2016 (Server Core installation)	`5094122 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019	`5094123 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019 (Server Core installation)	`5094123 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022	`5094128 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022 (Server Core installation)	`5094128 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2025	`5094125 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2025 (Server Core installation)	`5094125 (Security Update)`	Important	Elevation of Privilege	Yes

Patches

8 patches

Article	Type	Restart
`5094122`	Security Update	Yes
`5094123`	Security Update	Yes
`5094127`	Security Update	Yes
`5093998`	Security Update	Yes
`5094126`	Security Update	Yes
`5095051`	Security Update	Yes
`5094128`	Security Update	Yes
`5094125`	Security Update	Yes

Patch Diff

ghidriff · wininet.dll (KB5094126)

Integer overflow (CWE-190) leading to a use-after-free (CWE-416) in the Windows WinINet wininet.dll global cache-server reference counting, local EoP. WinINet's global cache server (CCacheServer) is reference-counted via process-global counters g_ulStrongReferences / g_ulWeakReferences; CCacheServer::StrongReferenceGlobalCacheServer / WeakReferenceGlobalCacheServer increment them and Strong/WeakReleaseGlobalCacheServer decrement, freeing the CCacheServer when the strong count reaches 0. PRE: the counters were 32-bit and incremented without an overflow check (g_ulStrongReferences = g_ulStrongReferences + 1), so a caller taking a very large number of references could wrap the 32-bit counter back to 0; a subsequent Release then observes count == 0 and frees the still-referenced CCacheServer - a reference-count overflow yielding a use-after-free of the cache server. Diff of wininet.dll 11.00.26100.8521 -> .8655 (Jun 9 2026, KB5094126) confirms the fix: gated behind CFR flag Feature_3431463225, the reference counters are widened to 64-bit (g_ullStrongReferences / g_ullWeakReferences) and the increment is saturated - if (!feature || count != 0xffffffffffffffff) count = count + 1 - so the count cannot wrap to 0, and access is serialized with AutoCritSec::Lock/Unlock; the release paths use the widened counters, closing the overflow-to-UAF.

Pre-patch version 11.00.26100.8521 Download

Post-patch version 11.00.26100.8655 Download

Function	Address	Change	Note
`CCacheServer::StrongReferenceGlobalCacheServer`	`code change`	code (64-bit + saturating refcount under lock, CFR-gated)	Pre: g_ulStrongReferences = g_ulStrongReferences + 1 (32-bit, unchecked). Post (Feature_3431463225): AutoCritSec::Lock; if (!feature \|\| g_ullStrongReferences != 0xffffffffffffffff) g_ullStrongReferences++ (64-bit, saturating); AutoCritSec::Unlock.
`CCacheServer::WeakReferenceGlobalCacheServer`	`code change`	code (64-bit + saturating weak refcount under lock, CFR-gated)	Same widening + saturation guard for g_ullWeakReferences under AutoCritSec lock.
`CCacheServer::StrongReleaseGlobalCacheServer / WeakReleaseGlobalCacheServer`	`code change`	code (use widened 64-bit counters)	Release paths decrement the widened g_ullStrongReferences / g_ullWeakReferences (frees CCacheServer when strong count reaches 0).
`CCacheServer::CCacheServer / Lock / Unlock`	`code change`	code (locking / condition-variable init)	Ctor and Lock/Unlock updated to initialize/use the critical section + condition variable guarding the counters.
`Feature_3431463225`	`gate`	added (CFR gate)	CFR flag gating the 64-bit saturating reference counting; the original 32-bit unchecked increment still ships when disabled.

View full diff report View RCA report

Attack Path

Overflowing the WinINet cache-server reference count wraps it to 0, freeing the still-referenced server

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

anonymous

References

MSRC Advisory MITRE NVD