Avira – Critical CSRF flaw Vulnerability puts millions users at risk

Egyptian bug hunter discovered that Avira Website is affected by CSRF flaw that allows attackers to hijack users’ accounts and access to their online backup.

What do you think about if tell you that an antivirus could represent a menace for your system? Antivirus like any other kind of software could be exploited by threat actors to compromise the machine as already explained my previous post.

The popular antivirus software Avira that includes a Secure Backup service is vulnerable to a critical web application vulnerability that could allow an attacker to take over the user’s account.

The Egyptian 16 year-old expert Mazen Gamal reported to The Hacker News that the Avira Website is affected by a CSRF (Cross-site request forgery) vulnerability that allows an attacker to hijack users’ accounts and access to their online secure cloud backup files.

The CSRF vulnerability potentially puts millions of Avira users’ account at risk.

CSRF allows an end user to execute unwanted actions on a web application once he is authenticated, in a typical attack scheme attacker sends a link via email or through a social media platform, or share a specially crafted HTML exploit page to trick the victim into executing actions of the attacker’s choosing.

In this specific case an attacker could use CSRF exploit to trick a victim into accessing a malicious link that contains requests which will replace victim’s email ID on Avira account with attacker’s email ID. This this CSRF attack the victim’s account could be easily compromised, by replacing the email address the attacker can easily reset the password of the victim’s account running the forget password procedure, bacause

Avira will send the password reset link to attacker’s email ID instead of the victim’s ID.

Once gained the access to the victim’s account the attacker would be able to retrieve its online backup, which include files the user has stored on the Online backup Software (https://dav.backup.avira.com/).

“I found a CSRF vulnerability in Avira can lead me to full account takeover of any Avira user account,” Gamal said via an email to The Hacker News. “The impact of the account takeover allowed me to Open the Backup files of the victim and also view the license codes for the affected user.”

Gamal also provided a Proof-of-Concept video to demonstrate its discovery.

Gamal has reported the vulnerability to the Avira Security Team on August 21th, the team admitted the flaw and fixed the CSRF bug on their website, but the Secure online backup service “is still vulnerable to hackers until Avira will not offer a offline password layer for decrypting files locally.”

Mazen Gamal has been recognized as an official bug hunter by Avira.

Pierluigi Paganini

(Security Affairs – AVIRA, CSRF)

Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.