External risk intelligence

Samsung Exynos SMS Processing Out-of-Bounds Write Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2025-62818

The vulnerability exists in baseband modem firmware processing SMS TP-UD packets. Mobile modems are designed to be public-facing by design in normal use, as they must receive and process cellular radio signals, including incoming SMS messages, directly from the mobile network without authentication or pre-authorization.

Out-of-bounds Write

Samsung Exynos 990 Firmware

Halo Surface Signal: 5 out of 5 — more likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability has been identified in Samsung's Exynos mobile and wearable processors and modems that could allow for unauthorized access and manipulation of device functions. This issue stems from how the system processes specific text message packets, creating an opening for potential system compromise. The main concern is to confirm if and how this impacts our deployed Samsung devices.

Flaw in Samsung processors, impacts phones and wearables.
Critical flaw: remote access possible via text messages.
Confirm exposure and understand business relevance.

Attack Path

How an attacker could exploit the issue

An attacker could trigger this vulnerability by sending a specially crafted SMS message to a vulnerable device. The flaw resides in how the modem firmware processes SMS packets, specifically an out-of-bounds write error caused by a mismatch in SMS data fields. This could allow an attacker to compromise the device's integrity and confidentiality.

No authentication required to send message.
Vulnerable component processes SMS packets.
High risk to confidentiality and integrity.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could impact Samsung mobile and wearable devices and modems. When processing specific SMS packets, an out-of-bounds write may occur, potentially affecting the system's integrity and confidentiality. The exact conditions and consequences depend on the specific device and its configuration.

System integrity and data confidentiality.
Malformed SMS packet processing.
Unauthorized system access or data exposure.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability resides in Samsung Exynos mobile and wearable processors, as well as modem firmware. Ownership likely falls to the device manufacturer's firmware team or potentially a platform/embedded systems team responsible for the core processor and modem components. The initial practical step involves identifying all Samsung devices utilizing the affected Exynos processors and modems within your environment, determining their network exposure, and verifying if they are business-critical.

Device manufacturer firmware team ownership.
Verify device network exposure.
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 software affected by CVE-2025-62818?

These are firmware components for Samsung mobile processors, wearable processors, and cellular modems, including various Exynos series (such as 980, 2400, and W1000) and specific modem models like the 5123 and 5400. This software manages core hardware communications, specifically handling cellular radio signals and incoming text message processing on mobile and wearable devices.

What is the weakness class for this vulnerability?

This CVE is categorized as an out-of-bounds write (CWE-787). In simple terms, the software makes a mistake while calculating memory space needed for incoming data. When processing an SMS packet, a mismatch in the TP-UDHI and UDL data fields causes the system to write data into an unauthorized memory location, which can compromise the device.

How is this vulnerability triggered?

An attacker triggers this by sending a specially crafted SMS message to a targeted device. The vulnerability is specifically located within the modem firmware's packet processing logic. It is important to note that sending a standard, properly formatted text message does not trigger this flaw; the exploit requires a malformed SMS packet designed to take advantage of the specific data field mismatch.

Is my device at risk based on Halo Surface Signal?

Halo Surface Signal identifies this as a high-risk concern because mobile modems are inherently internet-facing and public-facing by design. Because modems must constantly receive and process cellular radio signals, including incoming SMS messages, from the mobile network without needing any prior authentication or user interaction, any device with a vulnerable Exynos modem is exposed.

What should I do if I manage affected Samsung devices?

Your first step is to create an inventory of all devices in your environment that utilize the listed Exynos processors or modems. Once identified, prioritize these by their business criticality. Since this is a firmware-level issue, consult with the device manufacturer's security resources to track and plan for authorized firmware updates as they become available.

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.