CVE-2025-8699 Overview
CVE-2025-8699 is a critical insecure storage vulnerability affecting KioSoft "Stored Value" Unattended Payment Solutions. The vulnerability exists in the NFC payment card implementation, which utilizes vulnerable MiFare Classic cards to store account balances. Attackers with physical proximity can exploit this flaw to read, manipulate, and rewrite card data, enabling them to arbitrarily modify the monetary balance stored on the card and effectively generate fraudulent funds for purchasing goods.
Critical Impact
Attackers can manipulate NFC card balances to load up to $655.35 in fraudulent funds, enabling financial fraud and theft of goods from unattended payment terminals.
Affected Products
- KioSoft "Stored Value" Unattended Payment Solutions
- Systems utilizing MiFare Classic NFC cards for balance storage
Discovery Timeline
- 2025-09-12 - CVE CVE-2025-8699 published to NVD
- 2025-11-03 - Last updated in NVD database
Technical Details for CVE-2025-8699
Vulnerability Analysis
This vulnerability falls under CWE-922 (Insecure Storage of Sensitive Information). The fundamental security flaw lies in the design decision to store monetary balance information directly on client-controlled NFC cards rather than maintaining an authoritative server-side record. The MiFare Classic card technology, which has been widely documented as cryptographically weak, provides insufficient protection for the sensitive financial data stored within.
The attack methodology involves analyzing card memory dumps to identify the specific data fields containing cash value information. Through careful observation of changes between card states, an attacker can reverse-engineer the data structure and identify the balance storage location. Additionally, the implementation uses a simple XOR-based checksum mechanism that can be reverse-engineered by analyzing the relationship between the cash value field and other card data.
Root Cause
The root cause is the insecure storage of sensitive financial information (account balance) on an inherently vulnerable MiFare Classic NFC card. MiFare Classic's CRYPTO1 cipher has been publicly broken since 2008, allowing attackers to read and clone card contents with inexpensive, readily available hardware. Combined with a weak XOR-based integrity check rather than cryptographically secure authentication, this architecture fundamentally cannot prevent balance manipulation.
Attack Vector
The attack can be executed by an attacker with physical access to a legitimate stored value card and an NFC reader/writer device. The attacker performs the following steps:
- Card Acquisition: Obtain a legitimate KioSoft stored value NFC card
- Memory Extraction: Use an NFC reader to dump the complete card memory contents
- Balance Identification: Perform multiple transactions and compare memory dumps to identify which data fields correspond to the stored balance
- Checksum Analysis: Identify the XOR-based checksum mechanism by analyzing the relationship between balance values and the checksum field
- Balance Manipulation: Modify the balance field to a desired value (maximum $655.35) and recalculate the checksum
- Card Rewrite: Write the modified data back to the NFC card
- Exploitation: Use the manipulated card at unattended payment terminals to purchase goods with fraudulent funds
Due to the nature of this vulnerability involving hardware and proprietary payment systems, exploitation details are described in prose. For complete technical analysis, refer to the Sec-Consult Security Report.
Detection Methods for CVE-2025-8699
Indicators of Compromise
- Unusual transaction patterns showing cards with balances exceeding normal top-up limits
- Multiple high-value transactions from a single card in short time periods
- Cards with balance values approaching the $655.35 maximum that were never legitimately loaded
- Transaction logs showing purchases without corresponding top-up records in backend systems
Detection Strategies
- Implement server-side transaction monitoring to compare card-reported balances against authoritative backend records
- Deploy anomaly detection for cards exhibiting sudden unexplained balance increases
- Establish velocity checks on transaction frequency and volume per card
- Cross-reference point-of-sale transactions with top-up station activity logs
Monitoring Recommendations
- Enable comprehensive logging on all unattended payment terminals
- Implement real-time alerting for transactions exceeding configurable thresholds
- Regularly audit transaction discrepancies between terminal reports and backend financial systems
- Monitor for bulk purchases or unusual purchasing patterns at individual terminals
How to Mitigate CVE-2025-8699
Immediate Actions Required
- Contact KioSoft vendor support for guidance on available mitigations and upgrade paths
- Conduct a risk assessment of deployed unattended payment terminal environments
- Implement enhanced transaction monitoring and anomaly detection as an interim control
- Consider temporarily reducing per-transaction or daily spending limits on stored value cards
Patch Information
No vendor patch information is currently available in the NVD data. Organizations should monitor the Sec-Consult Security Report and contact KioSoft directly for remediation guidance. A fundamental fix requires migrating away from vulnerable MiFare Classic cards to more secure NFC technologies with proper cryptographic authentication.
Workarounds
- Implement server-side balance verification by maintaining authoritative balance records in a secure backend database and validating card-reported balances against these records for every transaction
- Deploy fraud detection rules to flag and review transactions with suspicious balance patterns before processing
- Consider transitioning to online-only transaction mode where all balance checks occur server-side
- Reduce maximum transaction values to limit financial exposure per compromised card
- Implement card blacklisting capabilities to rapidly disable suspicious cards
Mitigation for this vulnerability requires architectural changes to the payment system. The fundamental issue is the reliance on client-side balance storage without server-side verification. Until card technology is upgraded, implement compensating controls:
# Example monitoring configuration for transaction anomaly detection
# Configure logging and alerting thresholds in payment terminal management system
# These values should be adjusted based on normal business transaction patterns
MAX_TRANSACTION_VALUE=50.00
MAX_DAILY_TRANSACTIONS_PER_CARD=10
ALERT_BALANCE_THRESHOLD=500.00
ENABLE_REALTIME_MONITORING=true
LOG_ALL_TRANSACTIONS=true
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
