External risk intelligence

Samsung Exynos and Modem Out-of-Bounds Write via Malformed NAS Packets

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2025-27807

The vulnerability affects low-level firmware in Samsung mobile processors, wearable processors, and modems. These components handle internal device communications and baseband processing rather than being public-facing web or application services. Access typically requires proximity to the physical hardware or a specialized, non-standard attack vector, making public-internet-facing exploitation highly unlikely.

Out-of-bounds Write

Samsung Exynos 990 Firmware

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified within Samsung's mobile and wearable processors, as well as modems. This flaw could allow for unauthorized system access and control by exploiting malformed network packets. Understanding the potential impact and confirming relevance across our Samsung device fleet is key.

Flaw in Samsung processors and modems.
Critical vulnerability impacting device integrity.
Confirm device relevance and exposure.

Attack Path

How an attacker could exploit the issue

An attacker could target devices with specific Samsung processors by sending specially crafted network packets. This could lead to unauthorized memory writes within the device's modem component, potentially allowing for a denial-of-service condition or even remote code execution.

Network access required.
Malformed NAS packets trigger vulnerability.
Risk of denial-of-service or code execution.

Live Threat

Current exploitation, exposure, and threat context

The vulnerability could impact the internal operations of Samsung mobile processors, wearable processors, and modems. This occurs when malformed network packets are sent to the device, potentially leading to unexpected behavior or instability by overwriting memory beyond its intended boundaries.

Processor and modem firmware could be affected.
Malformed network packets could trigger the issue.
System instability or unexpected behavior may result.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability impacts Samsung Exynos processors, wearable processors, and modems. Given the nature of the affected technology, device manufacturers and mobile operators are likely responsible for firmware updates. The immediate first step is to identify all Samsung devices utilizing these processors and modems within your environment, assess their exposure and criticality, and then coordinate with Samsung or the device manufacturer for remediation.

Identify device owners and assess exposure.
Verify patch availability with Samsung/manufacturers.
Plan coordinated firmware updates.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the Samsung Exynos and modem technology involved here?

These are system-on-chip components and modem hardware used in a wide range of Samsung mobile devices and wearables. They function as the device's brain and cellular communications interface, managing core tasks like processing data, handling system instructions, and enabling network connectivity.

What does CWE-787 mean regarding CVE-2025-27807?

CWE-787 is the weakness class for an out-of-bounds write. In plain terms, the software fails to check the size of incoming data. This allows an attacker to write information into memory locations they should not have access to, which can corrupt the system, cause crashes, or permit unauthorized actions.

How is the vulnerability triggered by NAS packets?

The issue is triggered when the device processes a malformed Non-Access Stratum (NAS) packet. A standard, correctly formatted network packet will not trigger the bug; it specifically requires a crafted, malformed packet designed to exploit the missing length check during the communication process.

Do I need to worry about internet-facing exploitation?

According to Halo Surface Signal, this is very unlikely. Because the vulnerability exists within low-level firmware responsible for internal device operations rather than public-facing services, a remote attack over the public internet is not a typical vector. Exploitation generally requires proximity to the hardware or highly specialized attack conditions.

When should I take action for my Samsung devices?

Start by identifying which of your devices contain the listed Exynos or modem components. Once identified, monitor communications from your device manufacturer or mobile provider, as they are responsible for delivering the necessary firmware updates to resolve this issue on your specific hardware.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.