CVE-2026-40003: ZTE ZX297520V3 arbitrary memory write in BootROM

CVE-2026-40003 · Severity: medium · CVSS 5.1 · Published 2026-05-07

A security vulnerability exists in the startup code of the ZTE ZX297520V3 chipset, which is used in various telecommunications and networking hardware. An attacker with physical access to the device can use the USB port to bypass security protections that normally ensure only authorized software can run. This could allow an attacker to gain full control over the device, potentially leading to permanent modification of the hardware's behavior or unauthorized access to data processed by the device.

Vendors: Zte.

Quick answers

Is CVE-2026-40003 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-40003 being exploited in the wild.
How severe is CVE-2026-40003?
Medium severity, with a CVSS score of 5.1, published 7 May 2026.
Which products and versions are affected?
Zte Zx297520v3 Firmware All versions prior to May 2026 update.
Is there a fix for CVE-2026-40003?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-40003 attacked?
It is attacked with physical access, in device firmware.
Am I affected by CVE-2026-40003?
Check whether you run Zte Zx297520v3 or Zte Zx297520v3 Firmware at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The ZTE ZX297520V3 BootROM suffers from an out-of-bounds write vulnerability (CWE-787) due to insufficient validation of target addresses during USB download mode operations. By connecting to the device via USB, a physically present attacker can perform arbitrary memory writes to the BootROM runtime memory. This capability allows for stack smashing and control flow hijacking. Successfully exploiting this flaw enables the attacker to bypass Secure Boot signature verification, leading to the execution of unsigned, unauthorized code at the highest privilege level during the boot process.

Affected products

  • ZTE ZX297520V3 firmware All versions prior to May 2026 update

Timeline

  • 2026-05-07: advisory: Initial disclosure by ZTE Corporation

References

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