CVE-2025-71255 Overview
CVE-2025-71255 is an improper input validation vulnerability in the Modem IP Multimedia Subsystem (IMS) component disclosed in the Unisoc Product Security Bulletin. The flaw allows a remote attacker to trigger a denial of service condition without requiring authentication or user interaction. Exploitation does not grant additional execution privileges, but it can disrupt cellular service availability on affected devices. The issue is reachable over the network attack surface exposed by the IMS protocol stack handling.
Critical Impact
Remote attackers can cause a denial of service against the modem IMS subsystem with no privileges and no user interaction, impacting device availability.
Affected Products
- Unisoc-based platforms exposing the Modem IMS component (refer to the vendor bulletin for the specific chipset and firmware matrix)
- Mobile devices integrating the affected modem firmware
- Downstream OEM builds incorporating the vulnerable IMS stack
Discovery Timeline
- 2026-05-06 - CVE-2025-71255 published to NVD
- 2026-05-07 - Last updated in NVD database
Technical Details for CVE-2025-71255
Vulnerability Analysis
The vulnerability resides in the Modem IMS component, which handles IP Multimedia Subsystem signaling for voice and multimedia services over cellular networks. The component fails to properly validate input data received over the network, leading to a remote denial of service condition. The flaw is exploitable from the network without authentication or user interaction. Successful exploitation impacts availability only and does not affect confidentiality or integrity of device data.
IMS stacks parse signaling messages such as Session Initiation Protocol (SIP) and Session Description Protocol (SDP) payloads exchanged with carrier infrastructure. Improper validation in this layer typically allows malformed or unexpected fields to reach parsing routines that assume well-formed input. The result is an unhandled error path that crashes the modem service or forces a reset of cellular connectivity.
Root Cause
The root cause is improper input validation [CWE-20] within the Modem IMS message handling logic. The component accepts input without sufficient checks on structure, length, or value ranges before processing. The Unisoc bulletin does not publicly disclose the specific function or parsing routine involved.
Attack Vector
The attack vector is network-based. An attacker positioned to deliver crafted IMS signaling traffic to a target device, such as through a rogue base station, compromised carrier element, or interconnect abuse, can send malformed messages to trigger the condition. The attack complexity is low, and no authentication or user interaction is required.
No verified proof-of-concept code is publicly available. See the Unisoc Product Security Bulletin for vendor-supplied technical details.
Detection Methods for CVE-2025-71255
Indicators of Compromise
- Repeated unexpected modem resets or loss of cellular registration on affected devices
- Crash logs or ramdump artifacts referencing the IMS service or SIP/SDP parsing routines
- Anomalous IMS signaling traffic patterns originating from untrusted or unexpected network elements
Detection Strategies
- Correlate device telemetry for modem subsystem restarts with timing of inbound IMS signaling events
- Inspect carrier-side logs for malformed SIP/SDP messages directed at subscriber endpoints
- Monitor mobile device management (MDM) telemetry for elevated rates of cellular service loss across a fleet
Monitoring Recommendations
- Track firmware versions across managed mobile devices and flag those without the Unisoc patch applied
- Alert on repeated baseband or radio interface layer crashes within short time windows
- Validate carrier IMS perimeter filtering and log anomalies in signaling message structure
How to Mitigate CVE-2025-71255
Immediate Actions Required
- Apply the firmware update referenced in the Unisoc Product Security Bulletin as soon as it is available through OEM channels
- Inventory all mobile devices and embedded modules using affected Unisoc modem firmware
- Coordinate with carriers to confirm IMS perimeter filtering is enforced against malformed signaling
Patch Information
Unisoc has published advisory details in the Unisoc Product Security Bulletin. Device OEMs must integrate the corrected modem firmware into their over-the-air update channels. End users should install the latest available system update from their device manufacturer.
Workarounds
- Disable Voice over LTE (VoLTE) and Wi-Fi Calling features that rely on IMS where operationally acceptable until patched firmware is deployed
- Restrict device use on untrusted cellular networks where rogue base station risk is elevated
- Apply carrier-side filtering of malformed IMS signaling at the network edge
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
