CVE-2022-40538 in AR8035
Summary
by MITRE • 06/06/2023
Transient DOS due to reachable assertion in modem while processing sib with incorrect values from network.
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Analysis
by VulDB Data Team • 06/06/2023
This vulnerability represents a transient denial of service condition affecting modem firmware systems that process system information block (SIB) data from network sources. The flaw manifests as an assertion failure within the modem's processing logic when encountering SIB data containing malformed or unexpected values. The assertion mechanism, designed to detect programmatic errors or invalid states during runtime execution, becomes triggered when the modem receives SIB messages that do not conform to expected parameter ranges or data formats. This assertion failure causes the modem to terminate its current processing sequence and potentially restart its operational state, creating a temporary service interruption that disrupts ongoing communication sessions.
The technical implementation of this vulnerability resides in the modem's network protocol handling layer where SIB data is parsed and validated. When network entities transmit SIB messages containing values outside the acceptable parameter boundaries defined by the modem's internal validation routines, the assertion check fails and triggers an immediate system response. This behavior aligns with CWE-617, which describes reachable assertions that can be triggered by external inputs, and represents a classic example of insufficient input validation within telecommunication protocol stacks. The assertion failure typically occurs during the initial parsing phase of SIB data processing, where the modem validates received parameters against expected ranges or formats before proceeding with subsequent operations.
The operational impact of this vulnerability extends beyond simple service disruption to potentially affect network reliability and user experience in mobile communication environments. During the transient denial of service event, ongoing voice and data connections may experience temporary interruptions or complete disconnections, depending on the specific modem implementation and the timing of the assertion failure. Network operators may observe increased call setup failures, dropped connections, or reduced service availability in affected areas where devices encounter the malformed SIB data. The transient nature of the vulnerability means that the service disruption is temporary and typically resolves automatically once the modem completes its restart sequence or the problematic SIB data is no longer received, but this recovery period can vary significantly based on device implementation and network conditions.
Mitigation strategies for this vulnerability should focus on implementing robust input validation mechanisms within the modem's SIB processing logic to prevent assertion failures from occurring in response to malformed network data. Firmware updates that include enhanced error handling and graceful degradation capabilities are essential for addressing this issue, as they allow the modem to either discard invalid SIB data or process it without triggering critical assertion failures. Network operators should consider implementing network-side filtering mechanisms to identify and block malformed SIB messages before they reach affected modems, though this approach requires careful consideration of potential impact on legitimate network operations. The remediation process should also include comprehensive testing of modem firmware against various SIB data patterns to ensure that the validation logic properly handles edge cases and prevents assertion failures while maintaining normal operational functionality. Organizations should reference ATT&CK technique T1499.004 for network denial of service attacks when evaluating the broader threat landscape and implementing defensive measures.