CVE-2025-24056 — Windows Telephony Service Remote Code Execution Vulnerability

Executive Summary

Heap-based buffer overflow in Windows Telephony Server allows an unauthorized attacker to execute code over a network.

Overview

8.8

CVSS HIGH

Important

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Remote Code Execution

Weakness CWE-122: Heap-based Buffer Overflow

Released Mar 11 2025

Last Updated Mar 11 2025

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.01673 — 0.74751 percentile

NVD CVSS 8.8 HIGH — matches MSRC

CVSS Vector

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

ATTACK VECTOR

Network

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: 7.7

EPSS Score

0.01673

probability of exploitation in the next 30 days

0.74751 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

25 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 for 32-bit Systems	`5053618 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 for x64-based Systems	`5053618 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 1607 for 32-bit Systems	`5053594 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 1607 for x64-based Systems	`5053594 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 1809 for 32-bit Systems	`5053596 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 1809 for x64-based Systems	`5053596 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 21H2 for 32-bit Systems	`5053606 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 21H2 for ARM64-based Systems	`5053606 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 21H2 for x64-based Systems	`5053606 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 22H2 for 32-bit Systems	`5053606 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 22H2 for ARM64-based Systems	`5053606 (Security Update)`	Important	Remote Code Execution	Yes
Windows 10 Version 22H2 for x64-based Systems	`5053606 (Security Update)`	Important	Remote Code Execution	Yes
Windows 11 Version 22H2 for ARM64-based Systems	`5053602 (Security Update)`	Important	Remote Code Execution	Yes
Windows 11 Version 22H2 for x64-based Systems	`5053602 (Security Update)`	Important	Remote Code Execution	Yes
Windows 11 Version 23H2 for ARM64-based Systems	`5053602 (Security Update)`	Important	Remote Code Execution	Yes
Windows 11 Version 23H2 for x64-based Systems	`5053602 (Security Update)`	Important	Remote Code Execution	Yes
Windows 11 Version 24H2 for ARM64-based Systems 5053598 (Security Update) 5053636 (SecurityHotpatchUpdate) Important Remote Code Execution 5051987 5052105 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 10.0.26100.3476 10.0.26100.3403 Yes None Windows 11 Version 24H2 for x64-based Systems 5053598 (Security Update) 5053636 (SecurityHotpatchUpdate) Important Remote Code Execution 5051987 5052105 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 10.0.26100.3476 10.0.26100.3403 Yes None Windows Server 2008 for 32-bit Systems Service Pack 2 5053888 (Monthly Rollup) 5053995 (Security Only) Important Remote Code Execution 5052038 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.23168 Yes None Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) 5053888 (Monthly Rollup) 5053995 (Security Only) Important Remote Code Execution 5052038 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.23168 Yes None Windows Server 2008 for x64-based Systems Service Pack 2 5053888 (Monthly Rollup) 5053995 (Security Only) Important Remote Code Execution 5052038 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.23168 Yes None Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 5053888 (Monthly Rollup) 5053995 (Security Only) Important Remote Code Execution 5052038 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.23168 Yes None Windows Server 2008 R2 for x64-based Systems Service Pack 1 5053620 (Monthly Rollup) 5053627 (Security Only) Important Remote Code Execution 5052016 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.1.7601.27618 Yes None Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 5053620 (Monthly Rollup) 5053627 (Security Only) Important Remote Code Execution 5052016 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.1.7601.27618 Yes None Windows Server 2012	`5053886 (Monthly Rollup)`	Important	Remote Code Execution	Yes
Windows Server 2012 (Server Core installation)	`5053886 (Monthly Rollup)`	Important	Remote Code Execution	Yes
Windows Server 2012 R2	`5053887 (Monthly Rollup)`	Important	Remote Code Execution	Yes
Windows Server 2012 R2 (Server Core installation)	`5053887 (Monthly Rollup)`	Important	Remote Code Execution	Yes
Windows Server 2016	`5053594 (Security Update)`	Important	Remote Code Execution	Yes
Windows Server 2016 (Server Core installation)	`5053594 (Security Update)`	Important	Remote Code Execution	Yes
Windows Server 2019	`5053596 (Security Update)`	Important	Remote Code Execution	Yes
Windows Server 2019 (Server Core installation)	`5053596 (Security Update)`	Important	Remote Code Execution	Yes
Windows Server 2022 5053603 (Security Update) 5053638 (SecurityHotpatchUpdate) Important Remote Code Execution 5051979 5052106 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 10.0.20348.3328 10.0.20348.3270 Yes None Windows Server 2022 (Server Core installation) 5053603 (Security Update) 5053638 (SecurityHotpatchUpdate) Important Remote Code Execution 5051979 5052106 Base: 8.8 Temporal: 7.7 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 10.0.20348.3328 10.0.20348.3270 Yes None Windows Server 2022, 23H2 Edition (Server Core installation)	`5053599 (Security Update)`	Important	Remote Code Execution	Yes

Patches

8 patches

Article	Type	Restart
`5053618`	Security Update	Yes
`5053594`	Security Update	Yes
`5053596`	Security Update	Yes
`5053606`	Security Update	Yes
`5053602`	Security Update	Yes
`5053886`	Monthly Rollup	Yes
`5053887`	Monthly Rollup	Yes
`5053599`	Security Update	Yes

Patch Diff

ghidriff · tapisrv.dll (KB5053598)

Integer overflow leading to a heap-based buffer overflow (CWE-122) in the Windows Telephony Service tapisrv.dll priority-list readers, remote code execution on a client that connects to a malicious telephony server (Important, RCE, AV:N, UI:R, CVSS 8.8). GetPriorityList / GetMediaModesPriorityLists / LSetAppPriority build media-mode/app priority lists by allocating HeapAlloc(ghTapisrvHeap, value_size + 2) and filling it with value_size bytes (RegQueryValueExW), reserving 2 bytes for a wide terminator. PRE (.3037): the value_size <= value_size + 2 overflow check was gated behind Feature_1390216506 and BYPASSED when the flag was disabled, so a size near 0xFFFFFFFF made value_size + 2 wrap to a tiny allocation that was then overrun by the full-size copy - a heap overflow. Because the Telephony Service processes data from the telephony server the client connects to, MSRC classifies this as RCE on the client connecting to a malicious server. Diff of tapisrv.dll 10.0.26100.3037 -> .3323 (Mar 11 2025, KB5053598; vsize 380928 -> 372736, 25 funcs removed) confirms the fix: the fixed build enforces the value_size <= value_size + 2 overflow guard UNCONDITIONALLY (removing the Feature_1390216506 bypass) before the allocation and copy, and bounds the terminator write; LSetAppPriority also gains bounded 0x104/MAX_PATH app-name handling. Stated at confirmed-changed level (broad priority-list rework; the isolable mechanism is the always-enforced allocation overflow guard).

Pre-patch version 10.0.26100.3037 Download

Post-patch version 10.0.26100.3323 Download

Function	Address	Change	Note
`GetPriorityList / GetMediaModesPriorityLists`	`code change`	code (priority-list allocation overflow guard made unconditional)	Pre (.3037): HeapAlloc(value_size + 2) guarded by (Feature_1390216506 disabled \|\| value_size <= value_size + 2) - the overflow check was skipped when the flag was off, so a near-UINT_MAX value_size wrapped to a tiny allocation and was overrun. Post (.3323): value_size <= value_size + 2 enforced unconditionally before HeapAlloc and the RegQueryValueExW copy; terminator write bounded.
`LSetAppPriority`	`code change`	code (bounded app-name length handling)	Reworked with a 0x104/MAX_PATH-bounded length loop for the application-name string used to set priority.
`Feature_1390216506`	`gate`	gate (bypass removed)	Pre-patch this CFR flag gated the priority-list overflow check (bypassable when disabled); the fixed build enforces the check unconditionally.

View full diff report View RCA report

Attack Path

A malicious telephony server supplies an oversized priority-list value; the size+2 allocation overflows and the buffer is overrun

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