CVE-2026-20455: In geniezone, there is a possible out of bounds write due to a missing bounds check

Synopsis

An out-of-bounds write vulnerability exists in the GenieZone component of MediaTek chipsets (MT6739, MT6761, MT6765, MT6768), reachable from a local process that already holds System-level privilege. Because no bounds check is performed on a write operation, an attacker can corrupt memory beyond an intended buffer. Successful exploitation allows local escalation of privilege, giving the attacker control beyond the System privilege boundary. HarborGuard is tracking this advisory and will make a patched-image rebuild available the moment an upstream fix is published.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityNot required

  The attacker needs an existing shell or process on the host; no network path to the target is required.

• AuthenticationRequired

  A low-privilege (System-level) account is sufficient, but the attacker must already hold that account before exploiting the vulnerability.

• Victim interactionNot required

  No user action is needed; the exploit runs without any social-engineering or victim-triggered step.

• Attack complexityDetail

  Attack complexity is low, meaning the exploit is reliable and does not depend on race conditions, specific memory layouts, or other environmental factors.

Blast Radius

• Reads protected memory regions accessible beyond the System privilege boundary, potentially exposing credentials, keys, or sensitive runtime data.
• Writes arbitrary data outside the intended buffer, allowing modification of in-memory structures or persisted state controlled by higher-privilege components.
• Achieves local privilege escalation, granting the attacker capabilities beyond the System privilege level on the affected device.
• Disrupts integrity guarantees of the GenieZone trusted-execution environment, undermining isolation between normal-world and secure-world processes.