What is the CVSS score of CVE-2026-21549?

CVE-2026-21549 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 0.4%.

Which versions of Unisoc Modem are affected by CVE-2026-21549?

CVE-2026-21549 affects Unisoc modem firmware in numerous mobile devices and IoT endpoints (T8100, T9100, T8200, T8300 chipsets), enabling unauthenticated remote attackers to disable cellular…

How to fix or mitigate CVE-2026-21549?

Within 24 hours, inventory all devices across your organization that use Unisoc T8100, T9100, T8200, or T8300 modems-including smartphones, tablets, IoT devices, and connected equipment-working with procurement and IT teams to identify affected models and quantities. Within 7 days, contact all relevant device manufacturers and request patch timelines and interim guidance; evaluate whether network-based mitigations (segmentation, access controls, traffic filtering) can be applied to limit exposure for business-critical systems pending patches. Within 30 days, monitor Unisoc and OEM advisory channels for patch releases; establish a deployment plan for each device class; and prepare rapid-response procedures for firmware updates as they become available, prioritizing devices with highest operational criticality.

Unisoc Modem CVE-2026-21549

EUVD-2026-52230 HIGH

Improper Input Validation (CWE-20)

2026-08-03 Unisoc

GHSA-gg3c-vmg3-jg8j

Denial Of Service T8100 T9100 T8200 T8300 Unisoc Shanghai Technologies Co Ltd

7.5

CVSS 3.1 · Vendor: Unisoc

Severity by source

Vendor (Unisoc) PRIMARY

7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

vuln.today AI

7.5 HIGH

Modem receives over-the-air input remotely with no auth or interaction; impact is availability-only, scope unchanged.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (Unisoc).

CVSS VectorVendor: Unisoc

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Aug 03, 2026 - 08:24 vuln.today

CVE Published

Aug 03, 2026 - 07:18 cve.org

HIGH 7.5

DescriptionCVE.org

In modem, there is a possible improper input validation. This could lead to remote denial of service with no additional execution privileges needed

AnalysisAI

Remote denial of service in Unisoc modem firmware affects T8100, T9100, T8200, and T8300 chipsets through improper input validation. An unauthenticated remote attacker can send crafted network input to the modem component, causing an availability failure - effectively cutting off cellular connectivity on affected devices. No public exploit has been identified at time of analysis, and no KEV listing exists, but the CVSS:3.1/AV:N/AC:L/PR:N/UI:N profile means no preconditions limit the attacker's reach against any device using these chipsets.

Technical ContextAI

The vulnerability resides in the modem subsystem of Unisoc SoCs, specifically the T8100, T9100, T8200, and T8300 chipset families (CPE: cpe:2.3:a:unisoc_(shanghai)_technologies_co.,_ltd.:t8100/t9100/t8200/t8300:*:*:*:*:*:*:*:*). Modem firmware processes raw over-the-air protocol messages (e.g., LTE/NR RRC, NAS, or baseband-layer signaling) before any OS-level filtering occurs. Improper input validation - the broad root cause class implied by the description (no CWE was formally assigned) - means the modem fails to reject or safely handle malformed or out-of-specification network inputs, leading to a crash or hang of the modem subsystem. Unisoc is a Chinese semiconductor firm (formerly Spreadtrum/RDA) whose chipsets are widely deployed in budget Android smartphones and tablets, particularly in emerging markets. The scope unchanged (S:U) vector confirms the impact is confined to the modem component itself rather than escalating to the application processor.

RemediationAI

The primary remediation is to apply the firmware or software update issued by Unisoc and distributed by device OEMs, as referenced in the Unisoc security bulletin at https://www.unisoc.com/en/support/product-security-bulletin/2084109408382668801. No exact fixed firmware version number is specified in the available data; users should consult their device manufacturer's (OEM) security update channel for patched baseband firmware releases. Because baseband firmware updates are typically bundled into full Android OTA updates by OEMs, end users may need to wait for their device vendor to integrate and distribute the fix - a delay that commonly extends several weeks to months for budget-tier devices. In the interim, where operationally feasible, limiting device exposure to untrusted cellular networks (e.g., using Wi-Fi calling, disabling cellular data in high-risk environments, or avoiding untrusted roaming networks) reduces the attack surface, though these controls carry significant usability trade-offs. Network operators cannot directly mitigate device-side modem vulnerabilities.