CVE-2025-20725: Denial-of-Service Vulnerabilities in Mediatek Baseband Processors

Estimated reading time: 7 minutes

Key takeaways:

  • Multiple denial-of-service (DoS) vulnerabilities affect Mediatek baseband processors.
  • These vulnerabilities (CVE-2025-20725) stem from improper handling of SDP messages in VoLTE.
  • Exploitation leads to a crash in the baseband processor, causing a denial of service.
  • Input validation and secure coding practices are crucial to prevent such vulnerabilities.
  • PurpleOps services can help organizations proactively identify and address these risks.

Table of Contents

This blog post summarizes multiple denial-of-service (DoS) vulnerabilities affecting a wide range of Mediatek baseband processors. These vulnerabilities, collectively assigned CVE-2025-20725, stem from improper handling of Session Description Protocol (SDP) messages within Voice over LTE (VoLTE) implementations. Exploitation leads to a crash in the baseband processor, resulting in a denial of service. This poses a significant risk to devices relying on these processors for cellular connectivity. These flaws were identified by Taszk.io labs and affect numerous Mediatek chipsets. The vulnerabilities have been reported to Mediatek’s PSIRT team.

The vulnerabilities described below highlight the critical importance of proper input validation in baseband processors. Flaws in handling SDP messages can be exploited to cause significant disruptions in cellular communication.

Vulnerability Details

The following sections detail the specific vulnerabilities identified:

MSV-4629: Malformed Audio Attribute for RTP/AVP

  • Description: This vulnerability occurs within the sdp_msg_create_negotiation_sdp function. It is triggered by a malformed audio attribute associated with the Real-time Transport Protocol/Audio Video Profile (RTP/AVP). The malformed attribute leads to a NULL pointer access, causing the modem to crash.
  • Impact: Denial of service in the baseband processor, triggered by malformed VoLTE messages such as SIP INVITE or MESSAGE requests.
  • Technical Details: A crafted SIP message with a malformed ‘a=des:’ or ‘a=curr:x a b’ or ‘a=conf:x a b’ attribute for RTP/AVP triggers the vulnerability. This results in a NULL access during SDP processing, leading to a crash.
  • Example Payload:
INVITE sip:1 SIP/2.0
Content-Type: application/sdp
From: <sip:2>;tag=659747293
To: <sip:1>
CSeq: 1 INVITE

v=0
o=0 0 0 IN IP4 0
s=0
t=0 0
m=audio 0 RTP/AVP 0
a=des: & Bg %GAm

MSV-4628: NULL Dereference in sdp_msg_pack_media

  • Description: This vulnerability involves a NULL dereference within the sdp_msg_pack_media function. It arises when an SDP message contains a media element that is present in the original SDP structure but missing in a copied structure.
  • Impact: Denial of service in the baseband processor, triggered by malformed VoLTE messages such as SIP INVITE or MESSAGE requests.
  • Technical Details: The sdp_msg_create_negotiation_sdp function copies the SDP structure. However, the loop iterating through the media elements only checks for the end of the *original* structure, not the copied one. If a media element is missing in the copy, the loop continues using the original structure, eventually leading to a NULL pointer dereference.
  • Example Payload:
INVITE sip:192.168.101.2:50033;transport=tcp SIP/2.0
From: <sip:0010187046@ims.mnc001.mcc001.3gppnetwork.org>;tag=ttecbsI
To: "0010187049"<tel:0010187049;phone-context=ims.mnc001.mcc001.3gppnetwork.org>
CSeq: 1 INVITE
Content-Type: application/sdp
Content-Length: 784

v=0
o=0 0 0 IN IP4 0
s=0
t=0 0
m=application 0  0
m=application 0 RTP/AVP 0

MSV-4627: NULL Dereference During Parsing Empty SDP Bandwidth Field

  • Description: This vulnerability occurs during the parsing of an SDP bandwidth field. Specifically, if the bandwidth field is empty (e.g., b=), the parsing function may dereference a NULL pointer.
  • Impact: Denial of service in the baseband processor, triggered by malformed VoLTE messages such as SIP INVITE or MESSAGE requests.
  • Technical Details: The sdp_msg_unpack_bandwidth function uses strtok_r to parse the bandwidth field. If the field is empty, strtok_r returns NULL. Subsequent code doesn’t check for this NULL value and attempts to dereference it, leading to a crash.
  • Example Payload:
v=0
o=0 0 0 IN IP4 0
s=0
b=

Affected Devices

These vulnerabilities affect a wide range of Mediatek devices, including but not limited to:

MT6739, MT6761, MT6762, MT6762D, MT6762M, MT6763, MT6765, MT6765T, MT6767, MT6768, MT6769, MT6769K, MT6769S, MT6769T, MT6769Z, MT6771, MT6779, MT6781, MT6783, MT6785, MT6785T, MT6785U, MT6789, MT6813, MT6833, MT6833P, MT6835, MT6835T, MT6853, MT6853T, MT6855, MT6855T, MT6873, MT6875, MT6875T, MT6877, MT6877T, MT6877TT, MT6878, MT6878M, MT6879, MT6880, MT6883, MT6885, MT6886, MT6889, MT6890, MT6891, MT6893, MT6895, MT6895TT, MT6896, MT6897, MT6899, MT6980, MT6983, MT6983T, MT6985, MT6985T, MT6989, MT6989T, MT6990, MT6991, MT8666, MT8667, MT8673, MT8675, MT8676, MT8678, MT8765, MT8766, MT8766R, MT8768, MT8771, MT8781, MT8786, MT8788, MT8788E, MT8789, MT8791, MT8791T, MT8795T, MT8797, MT8798, MT8863, MT8873, MT8883, MT8893

Practical Takeaways

Technical Readers

  • Input Validation: When developing or auditing code that handles network protocols, rigorous input validation is essential. Always check for NULL pointers and handle malformed data gracefully to prevent crashes or unexpected behavior.
  • Fuzzing: Employ fuzzing techniques to identify potential vulnerabilities in protocol parsing code. Fuzzing can automatically generate a wide range of inputs, including malformed ones, to expose weaknesses in the code.
  • Secure Coding Practices: Adhere to secure coding practices to minimize the risk of vulnerabilities. This includes avoiding NULL pointer dereferences, handling errors properly, and using memory-safe functions.
  • SDP Auditing: When dealing with SIP and VoLTE implementations, carefully audit the SDP parsing logic. Pay attention to how different SDP attributes are handled, especially those related to media codecs and bandwidth.

Non-Technical Readers

  • Device Updates: Ensure that your devices receive regular security updates from the manufacturer. These updates often include patches for vulnerabilities like the ones described above.
  • VoLTE Security: Understand that VoLTE, while offering advantages in voice quality and data speeds, also introduces new security considerations. Vulnerabilities in VoLTE implementations can be exploited to disrupt communication.
  • Network Security: These baseband flaws are remotely exploitable via SIP messages, so maintain awareness that attacks can come in over the network, without any user interaction.

Relevance to PurpleOps Services

These vulnerabilities underscore the importance of comprehensive security assessments, supply-chain risk monitoring, and threat intelligence. PurpleOps offers services that can help organizations:

  • Supply-Chain Risk Monitoring: By monitoring for vulnerabilities in the components used in their products (such as Mediatek baseband processors), organizations can proactively identify and address potential risks. PurpleOps’s supply-chain risk monitoring service provides visibility into the security posture of third-party vendors and their products.
  • Cyber Threat Intelligence Platform: PurpleOps’s cyber threat intelligence platform provides real-time insights into emerging threats and vulnerabilities. This includes information about exploits targeting specific hardware and software components, allowing organizations to stay ahead of potential attacks.
  • Breach Detection: Early breach detection capabilities are crucial for mitigating the impact of successful exploits. PurpleOps can help organizations detect and respond to malicious activity on their networks before significant damage occurs, including abnormal behavior associated with exploitation attempts.
  • Dark Web Monitoring Service: Our dark web monitoring service can help identify discussions and activity related to the exploitation of these vulnerabilities, providing early warning and valuable context.
  • Underground Forum Intelligence: Accessing underground forums can reveal attacker tactics and techniques related to exploiting these Mediatek vulnerabilities.
  • Red Team Operations and Penetration Testing: PurpleOps can conduct PurpleOps Solutions to simulate real-world attacks and identify vulnerabilities in an organization’s security posture. This includes testing the resilience of devices using Mediatek baseband processors to attacks exploiting these SDP vulnerabilities.
  • Brand Leak Alerting: Monitor for potential leaks of sensitive information related to these Mediatek vulnerabilities, such as exploit code or configuration details.

These denial-of-service vulnerabilities in Mediatek baseband processors highlight the need for a layered security approach that includes robust input validation, proactive threat intelligence, and comprehensive security assessments. By leveraging PurpleOps’s services, organizations can better protect themselves against these and other emerging threats.

If you’re concerned about the security of your devices and infrastructure, and how vulnerabilities like CVE-2025-20725 could affect your organization, explore our services at https://www.purple-ops.io/platform/ or contact us for a consultation PurpleOps Solutions.

FAQ

Q: What is a denial-of-service (DoS) vulnerability?

A: A DoS vulnerability is a flaw in a system that can be exploited to make a service unavailable to legitimate users. In this case, the vulnerabilities cause the baseband processor to crash, disrupting cellular connectivity.

Q: What is an SDP message?

A: SDP (Session Description Protocol) is a text-based protocol used to describe multimedia communication sessions. It is commonly used in conjunction with SIP (Session Initiation Protocol) for establishing VoLTE calls.

Q: How can I protect my device from these vulnerabilities?

A: Ensure that your device receives regular security updates from the manufacturer. These updates often include patches for vulnerabilities like the ones described above.

Q: What is a baseband processor?

A: A baseband processor is a chip in a mobile device that handles all radio functions, including cellular communication. It is responsible for encoding and decoding signals transmitted over the cellular network.