CVE-2025-1698

Executive Summary

CVE-2025-1698 is a denial-of-service (DoS) vulnerability residing within the fingerprint sensor service component of an undocumented vendor product. The flaw manifests as a null pointer dereference, allowing a local attacker with low-privilege access to the targeted device to crash the service, thereby disabling biometric authentication functionality. While the NVD CVSS score is currently not assigned (N/A), the localized attack vector and availability impact suggest a medium-severity risk profile, though this is unconfirmed pending official scoring. The primary impact is an availability breach: the fingerprint sensor becomes unresponsive, potentially locking users out of devices that depend exclusively on biometric authentication and requiring administrative intervention for recovery. Patch status is uncertain (2/4 confidence) — a single unverified source claims a fix exists, but no vendor advisory or official patched version has been publicly identified.

Technical Analysis

The vulnerability is classified as a null pointer exception within the fingerprint sensor service. This is a classic memory safety flaw in the C/C++ family of languages, where a pointer is dereferenced without verifying it against NULL (or nullptr). In the context of a fingerprint sensor service, this typically occurs in the following code paths:

1. Input Validation Failure: When the service receives a malformed or unexpected input — such as a crafted inter-process communication (IPC) message, an invalid biometric template, or a corrupted sensor data payload — it may attempt to parse the data and assign the result to a pointer. If the parsing routine returns NULL (e.g., due to an unexpected format), the service subsequently dereferences that pointer in a downstream operation (e.g., copying data, calculating a hash, or updating a database), crashing the process.
2. Lifecycle Management Race: The service may maintain a global state object (e.g., SensorContext* ctx). If an operation is initiated before the context is initialized (or after it has been deallocated concurrently), the pointer is NULL at the time of dereference.
3. Resource Exhaustion Followed by Null: If the service allocates memory for a template and the allocation fails (returns NULL), subsequent use of that allocation without a check triggers the crash.

The attack surface is local, meaning the attacker must have a user account on the device and the ability to execute code or send commands to the fingerprint sensor service. On typical Android-based smartphones or embedded systems, this requires either a rooted/jailbroken device, an existing low-privileged app, or physical access via a debugging interface (e.g., ADB). The service likely runs with elevated privileges (often system or root in the sensor's Trusted Execution Environment or a privileged daemon), which makes the crash impactful but also means the attacker must already be inside the security boundary to a degree.

Because the vendor and product remain unspecified, the exact API surface (e.g., a /dev/fingerprint character device, a Binder service in Android, or a Unix socket) is unknown. However, the vulnerability class (null deref in a local service) is well-understood and trivially triggerable once the entry point is identified. The absence of an EPSS score and CWE ID further underscores the limited public technical detail.

Exploitation Scenarios

The following attack chain describes a generic but concrete exploitation path for a null pointer dereference in a local fingerprint sensor service. The scenario assumes an Android-style environment where the service is exposed via Binder IPC, but the steps translate to other Unix-like platforms with socket or ioctl interfaces.

Step 1 — Reconnaissance and Target Identification The attacker begins with a low-privileged shell on the target device (obtained via a separate vulnerability, social engineering, or physical access). They enumerate exposed services:

adb shell
# List Binder services
service list | grep -i fingerprint
# Or for Unix sockets:
ls -la /dev/*finger* /dev/*fp*
# Check for device nodes:
cat /proc/misc | grep -i finger

The attacker identifies the service name (e.g., fingerprintd) and its interface definition (e.g., from /system/framework/framework.jar or reverse-engineered .aidl files). They note the service's permission requirements and the data types it accepts — typically an array of bytes representing fingerprint templates.

Step 2 — Weaponing the Trigger The attacker crafts an IPC transaction designed to hit the null dereference. The most likely trigger is sending a malformed fingerprint template that passes initial length validation but contains a corrupted or empty payload, forcing the parsing routine to return a NULL pointer.

Using a compiled exploit or a scripting tool (e.g., spray or a custom C program using the Binder API), the attacker sends:

// Pseudo-code for Binder transaction
struct fingerprint_template {
    uint32_t length;
    uint8_t  data[0]; // variable
} __attribute__((packed));

// Case 1: Empty data with valid length header
uint8_t payload[0];
// Case 2: Length header says 100, but actual data is shorter (truncation)
uint8_t payload[10]; // claims length 100

The attacker iterates through boundary conditions:

• Zero-length arrays
• Length fields exceeding actual buffer size (truncated transaction)
• Null byte injection inside the data (causing a parser to abort and return NULL)

Step 3 — Payload / Execution The crafted IPC message is sent:

# Using a tool to invoke the service's "enroll" or "authenticate" method
fingerprint_service_client --op enroll --template /tmp/malformed.bin

Inside the service, the parsing function attempts to extract the template ID or hash. The parser fails, returns NULL, and the service dereferences it:

// Vulnerable pseudo-code inside service
FeatureVector* fv = parse_template(raw_data);
if (!fv) {
    // Parser returned NULL — but service does NOT check
    fv->normalize();  // CRASH: dereferences NULL
}

The process crashes with SIGSEGV (segmentation fault). The service restarts via init, but the attacker repeats the trigger in a loop, causing a crash cycle that renders the fingerprint sensor permanently unavailable.

Step 4 — Post-Exploitation Impact With the fingerprint service dead and potentially force-restarting in a crash loop, the device loses biometric authentication capability. Consequences include:

• Lockout: Users enrolled with fingerprint-only unlock are locked out if the device reboots (requiring password/PIN as fallback) — but if the service is critical to the boot chain (e.g., used for device encryption), the device may fail to boot entirely.
• Authentication Bypass for Others: In multi-user or enterprise-managed devices, forcing the fingerprint sensor offline may push the device into a "fail-open" or "fallback to weaker PIN" state, potentially weakening security policies.
• Physical Denial of Service: For devices where the fingerprint sensor is the sole user input (e.g., some kiosk systems), this constitutes a full physical DoS requiring manual maintenance.

Impact Assessment

The business impact is primarily availability related, per the vulnerability's classification. The CVSS vector is currently unassigned (N/A), so we cannot reference subscores; we assess the risk based on the attack vector (Local), attack complexity (Low — a crafted input is sufficient), privileges required (Low — a user-level account), and impact (High on availability, None on confidentiality/integrity). We project a reasonable CVSS base score in the 4.0–6.9 (Medium) range if scored.

• Affected Systems: Any device using the vulnerable fingerprint sensor service — smartphones, tablets, IoT access control panels, or enterprise laptops with fingerprint readers. The vendor is unknown, but the scope likely includes consumer and enterprise devices where the vendor has not publicly disclosed the issue.
• Blast Radius: A local attacker can crash the service. In shared-device environments (e.g., corporate-issued phones with MDM), the DoS could be used as a sabotage technique. On devices where the fingerprint service is part of the TEE (Trusted Execution Environment) stack, the crash may escalate beyond the user-space service into a full kernel or TEE panic, potentially requiring a hardware reset.
• Data Integrity/Confidentiality: Not directly impacted. The null deref does not allow code execution (in most modern mitigations, it is a crash, not a write primitive). However, a persistent crash loop can prevent a device from receiving security patches (if the update process relies on the sensor for user consent), lengthening exposure to other vulnerabilities.

Detection Guidance

Sigma Rule

title: Fingerprint Sensor Service Crash via Null Pointer Dereference
id: 2f6c4f8e-9a1b-4c5d-8e7f-0a1b2c3d4e5f
status: experimental
description: Detects repeated crashes of the fingerprint sensor service, indicative of CVE-2025-1698 exploitation
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-1698
tags:
    - attack.t1499.004
    - attack.t1204
author: Valtersit Threat Intelligence
date: 2025/06/12
logsource:
    product: linux
    service: system
detection:
    selection_crash:
        EventID: 7  # Sysmon process terminated
        Image|endswith: '/fingerprint_service'
        Description|contains: 'SIGSEGV'
    selection_restart:
        EventID: 4688  # New process (restart)
        NewProcessName|endswith: '/fingerprint_service'
    condition: selection_crash within 3 minutes followed by selection_restart
    timeframe: 15m
    condition: selection_crash (3 occurrences) and selection_restart
level: high
falsepositives:
    - Legitimate service restarts after system update
    - Rare crashes from hardware faults

YARA Rule

rule CVE_2025_1698_Fingerprint_Service_Exploit
{
    meta:
        author = "Valtersit Threat Intelligence"
        description = "Detects files or memory dumps containing exploit patterns for CVE-2025-1698 fingerprint service null deref"
        date = "2025-06-12"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-1698"
    strings:
        $s1 = "fingerprint_service" ascii wide nocase
        $s2 = "enroll" ascii wide nocase
        $s3 = "authenticate" ascii wide nocase
        $s4 = { 00 00 00 00 00 00 00 00 } // Null pointer pattern (8 zero bytes)
        $s5 = "SIGSEGV" ascii wide
        $s6 = "Template parse failed" ascii wide
    condition:
        uint16(0) == 0x5A4D and  // PE file
        (
            (1 of ($s1, $s2, $s3)) and
            (1 of ($s4, $s5, $s6))
        )
}

Suricata IDS Rule

alert ip any any -> any any (msg:"CVE-2025-1698 - Fingerprint Service Exploit Attempt (Null Deref)"; content:"|00 00 00 00 00 00 00 00|"; depth:64; within:128; reference:cve,2025-1698; classtype:attempted-dos; sid:20251698; rev:1; metadata:attack_target Local, deployment Perimeter, signature_severity Major, created_at 2025_06_12;)

Note: This rule is illustrative for network-level detection of binary payloads sent over remote channels (e.g., ADB over network, MDM agent channel). For purely local exploitation, host-based detection is primary.

Elastic Detection

// Detect repeated fingerprint service crashes within a 15-minute window
sequence by host.name with maxspan=15m
  [ process where process.name == "fingerprint_service" and event.outcome == "failure" and
    process.exit_code == 139 ]  // SIGSEGV
  [ process where process.name == "fingerprint_service" and event.action == "exec" ] * 3

// Alternative: Detect service crash followed by immediate restart attempts
sequence by process.entity_id with maxspan=1m
  [ process where process.name == "fingerprint_service" and event.action == "ended" and
    process.end == "signal" and process.signal == 11 ]
  [ process where process.name == "fingerprint_service" and event.action == "start" ]

Splunk SPL Query

index=linux sourcetype=linux_secure OR sourcetype=syslog
| where match(_raw, "fingerprint_service.*(segfault|SIGSEGV|signal 11|null pointer)")
| stats count as crash_count, values(_raw) as crash_logs by host, process_name
| where crash_count > 3
| eval threat_name = "CVE-2025-1698 Null Pointer Deref DoS"
| table _time, host, process_name, crash_count, crash_logs

// Detect process restart churn (indicates crash loop)
index=linux sourcetype=syslog
| eventstats dc(_time) as restart_count by host, process_name
| search process_name="fingerprint_service" AND event_action="process_started"
| where restart_count > 5
| table _time, host, process_name, restart_count

Wazuh OSSEC Rule

<group name="local_attacks,">
  <rule id="100168" level="12">
    <if_sid>530</if_sid>
    <match>fingerprint_service</match>
    <regex>segfault|SIGSEGV|null pointer|signal 11</regex>
    <description>CVE-2025-1698: Fingerprint service null pointer dereference crash detected on $(hostname)</description>
    <group>attack.denial_of_service,</group>
    <mitre>
      <id>T1499.004</id>
    </mitre>
    <options>no_full_log</options>
    <frequency>3</frequency>
    <timeframe>300</timeframe>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 2/4 — a single source claims a patch exists, but this is not independently confirmed. No official vendor advisory or CVE-mapped fix has been published.

1) Immediate Mitigations (valid until a verified patch is available)

• Restrict Local Access: Audit and limit local user accounts on affected devices. If the device supports it, remove the non-root user's ability to run arbitrary binaries (e.g., enforce SELinux enforcing mode with a policy that denies access to sensor device nodes /dev/*finger* for untrusted domains).
• Disable Automatic Restart of Sensor Service: In the service's init configuration (e.g., /init.rc), set restart to on-failure instead of always to prevent the crash loop from locking up the device permanently — allowing an admin to regain control after a single crash.
• Monitor for Crash Loops: Deploy the detection rules above (Sigma/Splunk/Wazuh) to alert on repeated fingerprint service crashes. Treat 3+ crashes within 15 minutes as an active exploitation attempt.
• Physical Security: If the device is an embedded/kiosk unit, implement tamper-evident enclosures to deter physical access that could trigger the flaw via ADB or serial console.

2) Patch / Upgrade Steps

• Verify Patch Existence: Check with your device OEM or system vendor for a hotfix related to "fingerprint sensor null pointer" or CVE-2025-1698. Since the vendor is unknown, contact your hardware supplier.
• Apply the Patch Once Available: The fix should add a NULL check after all parsing/allocation routines in the fingerprint service, e.g.:

  FeatureVector* fv = parse_template(raw_data);
  if (fv == nullptr) {
      log_error("Failed to parse template");
      return error_code;
  }
  fv->normalize();
  

• If No Patch is Confirmed: Since the flaw is local-only, consider replacing the fingerprint authentication method with a more mature implementation. On Android devices, update to the latest security patch level — Google's monthly bulletin often includes sensor service fixes from OEMs.

3) Long-Term Hardening

• Use AddressSanitizer (ASan) in the vendor's development pipeline to catch null derefs before release.
• Enable Memory Tagging Extension (MTE) on ARM devices, which provides hardware-assisted detection of invalid memory accesses, turning the exploitable crash into a detectable security event.
• Segment the Sensor Service: Run the fingerprint service in a separate, seccomp-filtered sandbox with no access to sensitive user data, limiting impact if it crashes.
• Establish a Threat Intel Feed: Subscribe to vendor CVE updates and the NVD RSS feed for CVE-2025-1698 to receive the official patch release time.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2025-1698 — (Note: limited metadata; score pending)
2. US-CERT CISA KEV: CVE-2025-1698 is NOT in CISA's Known Exploited Vulnerabilities catalog as of this writing. Monitor https://www.cisa.gov/known-exploited-vulnerabilities-catalog for updates.
3. FIRST EPSS: Not yet scored — check https://www.first.org/epss/ regularly for an open-source probability score.
4. MITRE ATT&CK: T1499.004 — "Endpoint Denial of Service: Application Exhaustion Flood" is the closest mapping. See https://attack.mitre.org/techniques/T1499/004/.
5. Exploit Status: No public PoC or Nuclei template identified. No threat actor campaigns have been observed in the wild. This does not preclude private exploitation; maintain vigilance.

Threat actor campaigns / in-the-wild evidence: None confirmed. The vulnerability is local-only, which significantly reduces the likelihood of mass exploitation. However, targeted physical-access attacks against specific individuals (e.g., corporate executives, government personnel) could use this to disable biometric lockout on a stolen device. Organizations handling biometric authentication infrastructure should prioritize patch verification for any device in their fleet that uses fingerprint readers.