CVE-2026-27748
Improper Link Resolution in Avira Updater Enables Privilege Escalation
Publication date: 2026-03-05
Last updated on: 2026-04-01
Assigner: VulnCheck
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| avira | internet_security | to 1.1.114.3113 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-59 | 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. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
[{'type': 'paragraph', 'content': "CVE-2026-27748 is an arbitrary file deletion vulnerability in Avira Internet Security's Software Updater component. The updater runs with SYSTEM privileges and deletes files under C:\\ProgramData during its update process without checking if the file path is a symbolic link or reparse point."}, {'type': 'paragraph', 'content': 'A local attacker with limited privileges can create a malicious symbolic link that redirects the deletion operation to any file they choose. This causes the updater to delete attacker-selected files with SYSTEM-level privileges.'}, {'type': 'paragraph', 'content': 'This improper link resolution flaw can lead to local privilege escalation, denial of service, or compromise of system integrity depending on which files are targeted and the operating system configuration.'}] [1, 3]
How can this vulnerability impact me? :
The vulnerability allows a local attacker to delete arbitrary files with SYSTEM privileges, which can have several impacts:
- Local Privilege Escalation: By deleting specific system files, an attacker can escalate their privileges to SYSTEM level.
- Denial of Service: Deleting critical files can disrupt system or application functionality, causing denial of service.
- System Integrity Compromise: Deletion of important files can compromise the integrity and stability of the operating system.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability can be detected by monitoring the Software Updater component of Avira Internet Security for suspicious file deletion activities, especially deletions under the C:\ProgramData directory involving symbolic links.
Using tools like Process Monitor (Procmon) can help confirm if files are being deleted with SYSTEM privileges through symbolic links.
Additionally, testing for the presence of malicious symbolic links can be done using symbolic link testing tools such as those developed by James Forshaw.
- Run Process Monitor to filter for file delete operations by the Avira Software Updater service targeting C:\ProgramData.
- Use command line to list symbolic links under C:\ProgramData, for example: `dir /AL /S C:\ProgramData` to identify suspicious links.
- Use PowerShell to find symbolic links: `Get-ChildItem -Path C:\ProgramData -Recurse -Attributes ReparsePoint`.
What immediate steps should I take to mitigate this vulnerability?
Immediate mitigation steps include preventing local attackers from creating symbolic links in the C:\ProgramData directory and restricting permissions to this directory to trusted users only.
Applying any available patches or updates from Avira Internet Security that address this vulnerability is critical.
Monitoring and auditing file deletion operations by the Software Updater service can help detect exploitation attempts.
- Restrict user permissions to prevent creation of symbolic links in sensitive directories.
- Update Avira Internet Security to the latest version that fixes this vulnerability.
- Use monitoring tools like Process Monitor to audit file deletions by SYSTEM processes.