A critical security vulnerability has been discovered in Zendesk’s Android SDK implementation that allows attackers to perform mass account takeovers without any user interaction.
The flaw, which earned a $3,000 bug bounty payout, stems from predictable token generation mechanisms that enable unauthorized access to all Zendesk support tickets across affected organizations.
Key Takeaways
1. Predictable JWT tokens in Zendesk’s Android SDK allow zero-click account takeovers.
2. Attackers can mass-generate tokens without rate limits to access all tickets and data.
3. Fix by using high-entropy secrets, enforcing rate limits, and auditing mobile auth.
The vulnerability exploits a fundamental weakness in how the Zendesk Android SDK generates authentication tokens, combining hardcoded secrets with sequential account IDs to create predictable JWT tokens.
This design flaw allows malicious actors to systematically generate valid authentication tokens for any user account without requiring any form of user interaction or social engineering.
Account Takeover Vulnerability
Voorivex’s Team reports that the vulnerability lies within the ZendeskHelper.g() method, which implements a flawed token generation algorithm. The method creates authentication tokens using a predictable formula:
The token generation process follows these steps:
- Base String Construction: REDACTED-{AccountID}-{HardcodedSecret}
- SHA-1 Hash Generation: The base string is processed through SHA-1 hashing
- Final Token Format: {AccountID}_{SHA1Hash}
The critical flaw emerges from two key weaknesses: the use of a static hardcoded secret (987sdasdlkjlakdjf) that remains constant across all installations, and sequential account IDs (getRemoteId()) that can be easily enumerated.
This combination creates a scenario where attackers can generate valid authentication tokens for any user by simply iterating through account ID ranges.
The authentication flow sends POST requests to /access/sdk/jwt endpoints:
The server responds with a valid access_token that grants full access to the victim’s Zendesk support environment, including the ability to read all tickets, submit new requests, and perform any action available through the support interface.
The vulnerability enables zero-click mass account takeover attacks through systematic token generation and validation.
Attackers can implement automated scripts to iterate through account ID ranges, generate corresponding tokens, and validate them against Zendesk endpoints without triggering rate limiting or account lockout mechanisms.
Successful exploitation grants attackers access to:
- Complete ticket histories containing sensitive customer communications
- Personal identifiable information (PII) within support conversations
- Internal company communications and support procedures
- Customer complaint patterns and business intelligence data
- Ability to impersonate legitimate users in support interactions
The vulnerability affects any organization using Zendesk’s Android SDK for mobile support integration, potentially impacting thousands of companies worldwide.
This critical flaw demonstrates the severe security risks associated with predictable authentication mechanisms and highlights the importance of implementing robust token generation systems and comprehensive security testing throughout the mobile application development lifecycle.
Find this Story Interesting! Follow us on LinkedIn and X to Get More Instant Updates.
Source link
