CVE-2025-21421 Overview
CVE-2025-21421 is a memory corruption vulnerability affecting a broad range of Qualcomm firmware components, including Snapdragon compute platforms, FastConnect connectivity subsystems, and WCD/WSA audio codec firmware. The flaw resides in an application programming interface (API) that processes escape codes, where insufficient bounds handling leads to memory corruption. The weakness is classified as [CWE-126] (Buffer Over-read). A local, authenticated attacker with low privileges can trigger the condition to compromise confidentiality, integrity, and availability on the affected device. Qualcomm addressed the issue in the Qualcomm April 2025 Security Bulletin.
Critical Impact
Successful exploitation can corrupt memory in privileged firmware components, enabling code execution or system compromise on affected Snapdragon-based endpoints and connectivity devices.
Affected Products
- Qualcomm Snapdragon 8cx Gen 2 and Gen 3 Compute Platforms (SC8180X, SC8280XP series)
- Qualcomm FastConnect 6200/6700/6800/6900/7800 connectivity firmware
- Qualcomm WCD93xx audio codec and WSA88xx smart speaker amplifier firmware
Discovery Timeline
- 2025-04-07 - CVE-2025-21421 published to the National Vulnerability Database (NVD)
- April 2025 - Qualcomm releases fixes in the April 2025 Security Bulletin
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-21421
Vulnerability Analysis
The vulnerability is a memory corruption condition triggered during processing of escape codes in a Qualcomm API. Escape code parsers typically iterate through a byte stream looking for control sequences that alter interpretation of subsequent input. When the parser fails to validate the length or structure of an escape sequence against the underlying buffer, subsequent reads or writes can extend beyond allocated memory. The Common Weakness Enumeration classification [CWE-126] describes a buffer over-read, where the routine reads past the end of the intended buffer.
Because the affected code executes inside firmware running on Qualcomm system-on-chip components, corruption can influence execution paths in privileged contexts. The attack requires local access and low privileges but no user interaction, and it impacts confidentiality, integrity, and availability.
Root Cause
The root cause is improper bounds handling in the API responsible for parsing escape codes. The parser advances through input without confirming that each escape sequence remains within the caller-supplied buffer. When a malformed or oversized escape token is supplied, the routine reads or writes outside the expected memory region, producing memory corruption.
Attack Vector
An attacker with local access and low privileges on an affected device can invoke the vulnerable API with crafted input containing malicious escape codes. The attacker does not need user interaction. Because the flaw is exposed by an API surface reachable from a lower-privileged context, unprivileged applications on affected Snapdragon-based devices are a realistic path to trigger the condition. See the Qualcomm April 2025 Security Bulletin for the full component listing.
No public proof-of-concept exploit code has been released for CVE-2025-21421 at the time of writing.
Detection Methods for CVE-2025-21421
Indicators of Compromise
- Unexpected crashes, kernel panics, or firmware resets on Snapdragon-based devices, particularly following invocation of low-level driver or audio APIs
- Unexplained privilege transitions or unsigned processes accessing Qualcomm driver interfaces
- Firmware or driver components running at revisions predating the April 2025 Qualcomm patch level
Detection Strategies
- Inventory endpoints, laptops, and embedded devices using the affected Qualcomm firmware, then correlate against the patched build levels listed in the vendor bulletin
- Enable crash and telemetry logging on Snapdragon compute platforms to identify repeated faults in driver stacks that touch the vulnerable API
- Monitor for local processes making anomalous IOCTL or API calls into Qualcomm audio, connectivity, or platform firmware components
Monitoring Recommendations
- Aggregate operating system crash reports and Windows Error Reporting (WER) or Linux kdump output into a centralized log platform for triage
- Track firmware and driver version drift across managed fleets to confirm patch adoption
- Alert on installation or execution of unsigned binaries that interact with Qualcomm HLOS driver interfaces
How to Mitigate CVE-2025-21421
Immediate Actions Required
- Apply the firmware and driver updates referenced in the Qualcomm April 2025 Security Bulletin via the appropriate OEM update channel
- Prioritize patching Snapdragon-based laptops, tablets, and IoT devices that expose the affected APIs to untrusted local users
- Restrict local application install rights on affected devices until patches are deployed
Patch Information
Qualcomm published fixes in the April 2025 Security Bulletin. Because the affected components ship as firmware and drivers integrated by device OEMs, patches typically arrive through Windows Update, Android security updates, or vendor-specific update tooling. Confirm that the delivered platform build meets or exceeds the level listed in the Qualcomm advisory.
Workarounds
- No vendor-supplied workaround has been published; apply the patched firmware as soon as OEM updates are available
- Reduce local attack surface by enforcing application allow-listing and removing standard user access to development or debugging interfaces
- Isolate unpatched devices from sensitive networks and data until updates are installed
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
