Introduction
Remote heap overflows in baseband processors have historically enabled attackers to compromise devices at the cellular protocol level, bypassing OS-level defenses. CVE-2025-54329 affects a wide range of Samsung Exynos mobile processors, wearable chipsets, and modems, exposing millions of devices to potential memory corruption via malformed NAS messages. The vulnerability is significant because it targets the Non-Access Stratum (NAS) layer, which is responsible for critical signaling and SMS delivery in LTE and 5G networks.
About Samsung Exynos and NAS: Samsung is one of the world's largest semiconductor manufacturers, with its Exynos line powering flagship smartphones, wearables, and network equipment globally. The NAS protocol stack is a foundational component in mobile communications, handling signaling and SMS outside of the IP stack. Vulnerabilities in this layer can have far-reaching impacts across consumer and enterprise devices.
Technical Information
CVE-2025-54329 is a heap-based buffer overflow in the NAS component's function for sending multiple payload messages, including SMS. The vulnerability exists because the function does not perform adequate bounds checking when handling multiple payloads. Specifically, when a NAS message is constructed with multiple payloads, the function fails to verify that the total size of all payloads fits within the allocated heap buffer. An attacker who can send crafted NAS messages (for example, via a compromised or rogue base station) can trigger a heap overflow by specifying excessive payload sizes or counts.
The root cause is improper validation of input parameters and miscalculation of buffer boundaries during message segmentation and reassembly. The vulnerable code is present in the NAS implementation of the following Exynos and modem models:
- Exynos 980
- Exynos 990
- Exynos 850
- Exynos 2100
- Exynos 1280
- Exynos 2200
- Exynos 1330
- Exynos 1380
- Exynos 1480
- Exynos 2400
- Exynos 1580
- Exynos 2500
- Exynos W920
- Exynos W930
- Exynos W1000
- Modem 5123
- Modem 5300
- Modem 5400
No public code snippets of the vulnerable function are available. The vulnerability is classified as CWE-122 (Heap-based Buffer Overflow).
Patch Information
To address the heap overflow vulnerability identified in CVE-2025-54329, Samsung has implemented a patch that introduces strict bounds checking within the function responsible for sending multiple payload messages, including SMS. This enhancement ensures that the function verifies the size of each payload before processing, thereby preventing buffer overflows that could lead to memory corruption.
The core of the patch involves adding a conditional check to validate the payload size against the allocated buffer size. If the payload exceeds the permissible limit, the function will return an error, effectively halting the process and safeguarding the system from potential exploitation.
While the exact code modifications are proprietary and not publicly disclosed, the general approach can be illustrated as follows:
// Pseudo-code representation of the patch if (payload_size > MAX_PAYLOAD_SIZE) { return ERROR_CODE; } // Proceed with processing the payload
By incorporating this bounds checking mechanism, the patch mitigates the risk of heap overflow attacks by ensuring that all payloads are within the acceptable size range before processing. This proactive measure enhances the overall security and stability of the affected components.
For detailed information and official statements regarding the patch, please refer to Samsung's security update page: https://semiconductor.samsung.com/support/quality-support/product-security-updates/cve-2025-54329/
Affected Systems and Versions
CVE-2025-54329 affects the following Samsung Exynos processors and modems:
- Exynos 980
- Exynos 990
- Exynos 850
- Exynos 2100
- Exynos 1280
- Exynos 2200
- Exynos 1330
- Exynos 1380
- Exynos 1480
- Exynos 2400
- Exynos 1580
- Exynos 2500
- Exynos W920
- Exynos W930
- Exynos W1000
- Modem 5123
- Modem 5300
- Modem 5400
All firmware versions for these models prior to the November 2025 security update are vulnerable. Devices running the November 2025 security update or later are not affected.
Vendor Security History
Samsung Exynos processors have previously been affected by similar heap overflow vulnerabilities in their NAS and baseband protocol implementations. Notable examples include CVE-2023-21517 (heap buffer overflow in LTE ESM) and vulnerabilities in LLC and RLC layers disclosed in 2023. Samsung typically issues monthly security updates and coordinates advisories through its semiconductor security portal. The company has improved patch response times in recent years, but the diversity of affected products can result in staggered update rollouts.
