CVE-2026-12520 zephyrproject CVE debrief

Who should care

Organizations using the Sierra Wireless HL7800 cellular modem driver, particularly those in industries relying on cellular connectivity, should prioritize patching this vulnerability. The potential for kernel-side code execution makes this a critical concern for system administrators and security teams.

Technical summary

The Sierra Wireless HL7800 cellular modem driver has a stack buffer overflow vulnerability due to improper use of net_buf_linearize(). The +KCELLMEAS handler allows for a full stack buffer overflow potentially leading to code execution in kernel context. The bug is caused by writing a NUL terminator past the end of a 128-byte stack buffer. An attacker can exploit this by causing the modem to emit an over-long AT response line.

Defensive priority

This vulnerability allows for a potential stack buffer overflow in the Sierra Wireless HL7800 cellular modem driver, which could lead to code execution in kernel context. Affected systems should prioritize patching due to the high complexity of exploitation and potential for kernel-side corruption.

Recommended defensive actions

• Apply patches or updates provided by the vendor to fix the vulnerability
• Review and update affected systems to ensure the fix is deployed
• Monitor for potential exploitation attempts
• Implement compensating controls to detect and prevent similar attacks
• Perform a thorough review of the affected systems' configurations and ensure that they align with security best practices
• Track exceptions and retest remediated assets to ensure the vulnerability is fully resolved
• Continuously monitor for potential exploitation attempts and adjust security controls as needed

Evidence notes

The CVE details a stack buffer overflow vulnerability in the Sierra Wireless HL7800 cellular modem driver. The bug arises from the misuse of net_buf_linearize() which can lead to out-of-bounds writes. The +KCELLMEAS handler is particularly vulnerable, allowing for a full stack buffer overflow potentially leading to code execution in kernel context. Evidence is based on official CVE and NVD records, as well as source references from the Zephyr project.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.