CVE-2026-25255: gRPC Server Privilege Escalation Vulnerability

CVE-2026-25255 Overview

CVE-2026-25255 is a local privilege escalation vulnerability caused by an exposed dangerous function in a gRPC server component addressed in the Qualcomm May 2026 security bulletin. A local, authenticated attacker with low privileges can invoke the exposed function through the gRPC interface to gain elevated permissions on the affected device. The flaw is classified under CWE-749, Exposed Dangerous Method or Function. Successful exploitation impacts confidentiality, integrity, and availability, and the scope change indicates the attacker can affect resources beyond the vulnerable component.

Critical Impact
A local attacker with low privileges can invoke an exposed gRPC function to escalate privileges and compromise components outside the vulnerable service's security scope.

Affected Products

Qualcomm components referenced in the Qualcomm Security Bulletin May 2026
Specific product and version identifiers were not enumerated in the NVD entry at time of publication
Refer to the vendor advisory for the full list of impacted chipsets and software packages

Discovery Timeline

2026-09-22 - CVE-2026-25255 published to NVD
2026-09-22 - Last updated in NVD database

Technical Details for CVE-2026-25255

Vulnerability Analysis

The vulnerability resides in a gRPC server that exposes a sensitive function without adequate access control. gRPC is a high-performance remote procedure call framework commonly used for inter-process and inter-service communication on device platforms. When a service exposes a method that performs privileged actions without validating the caller's authorization, any local process that can reach the gRPC endpoint can invoke it.

A low-privileged local process can connect to the gRPC endpoint and invoke the dangerous function. Because the function performs actions that require higher privileges than the caller possesses, the invocation results in privilege escalation. The scope change described in the vulnerability metrics indicates the attacker can influence resources beyond the boundaries of the vulnerable gRPC service.

Root Cause

The root cause is an improperly protected method exposed through a gRPC interface, classified as CWE-749. The service exports a function that performs privileged operations but does not enforce authorization checks on the caller. Design assumptions that only trusted components would communicate with the endpoint are not enforced at the API boundary.

Attack Vector

The attack requires local access and low privileges. An attacker executes code on the target device, discovers the gRPC endpoint, and issues a crafted request to invoke the exposed dangerous function. No user interaction is required. The vulnerability is typically reachable from a malicious mobile application or a compromised local service running on the same device. Technical details beyond the summary are not disclosed in the NVD entry; consult the Qualcomm Security Bulletin May 2026 for vendor-specific information.

Detection Methods for CVE-2026-25255

Indicators of Compromise

Unexpected local processes establishing connections to gRPC service endpoints on affected devices
Privileged operations initiated by processes that normally lack the required permissions
Anomalous invocation patterns against internal RPC interfaces used by system services

Detection Strategies

Audit access logs on gRPC service endpoints and correlate caller identity with expected client processes
Monitor for privilege transitions where a low-integrity process triggers actions typically executed by system-level components
Instrument the gRPC server to log all method invocations along with the authenticated caller's UID or client identifier

Monitoring Recommendations

Collect device telemetry that captures inter-process communication with system services and forward to a centralized analytics platform
Baseline legitimate callers of the affected gRPC methods and alert on deviations
Review installed application inventories on managed devices for untrusted software with local execution capability

How to Mitigate CVE-2026-25255

Immediate Actions Required

Apply the vendor security updates referenced in the Qualcomm Security Bulletin May 2026 as soon as OEM firmware becomes available
Restrict installation of untrusted third-party applications on affected devices until patches are deployed
Inventory devices using affected Qualcomm components and prioritize update deployment

Patch Information

Qualcomm addressed the vulnerability in the May 2026 security bulletin. Downstream device vendors integrate the fix into OEM firmware releases. Verify the patch level on managed devices matches or exceeds the version identified in the vendor advisory.

Workarounds

No vendor-supplied workaround is documented in the NVD entry; patch deployment is the recommended remediation
Reduce local attack surface by limiting sideloaded applications and enforcing application allowlisting through mobile device management
Monitor for the release of OEM firmware updates that incorporate the Qualcomm patch and schedule accelerated rollout

bash

# Verify device firmware patch level against the vendor advisory
# Example (Android): confirm ro.build.version.security_patch is 2026-05-01 or later
adb shell getprop ro.build.version.security_patch