# CVE-2026-77178: Oracle VM VirtualBox heap out-of-bounds write in PCNet emulation

Source: https://junglewise.ai/threats/cve-2026-77178-oracle-vm-virtualbox-before-7-2-8-allows-guest-os-users-to-cause  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-06. Updated: 2026-10-06  
License: CC BY 4.0 with a link back

CVE-2026-77178 · Severity: info · Published 2026-10-06

Oracle VM VirtualBox's PCNet network device emulation contains a heap memory vulnerability that allows a malicious guest operating system to write data past a buffer boundary in the host process. An attacker with control of a guest VM can corrupt adjacent host memory, potentially leading to host system compromise or denial of service. This is a guest-to-host privilege escalation vector in virtualized environments.

Technologies: [Oracle Vm Virtualbox](https://junglewise.ai/threats/technologies/virtualbox). Vendors: [Oracle](https://junglewise.ai/threats/vendors/oracle).

## Quick answers

**Is CVE-2026-77178 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77178 being exploited in the wild.

**How severe is CVE-2026-77178?** Informational severity, published 6 October 2026.

**Which products and versions are affected?** Oracle Vm Virtualbox before 7.2.8.

**Is there a fix for CVE-2026-77178?** Yes: fixed in 7.2.8. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-77178 attacked?** It is attacked from the adjacent network, in a network appliance.

**Am I affected by CVE-2026-77178?** Check whether you run Oracle Vm Virtualbox 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.

## How to fix

- Fixed in 7.2.8

## Technical details

The vulnerability is a bounded heap out-of-bounds write in the pcnetReceiveNoSync function (DevPCNet.cpp) of the PCNet (Am79C970A) network device model. A guest can exploit internal loopback mode with chained transmit descriptors to send a 4096-byte frame into a 4088-byte receive buffer (positioned at offset +8), causing guest-controlled data to overwrite adjacent device state. The flaw was fixed in version 7.2.8 by repositioning the write cursor to the buffer base.

## Affected products

- Oracle VM VirtualBox before 7.2.8

## Timeline

- 2026-10-06: disclosed

## References

- [https://gist.github.com/entropy1337/cd0d5b368445d20c43aca2590b313892](https://gist.github.com/entropy1337/cd0d5b368445d20c43aca2590b313892)
- [https://www.oracle.com/](https://www.oracle.com/)

## Related threats

- [Oracle VM VirtualBox core privilege escalation via physical network access](https://junglewise.ai/threats/cve-2026-87322-vulnerability-in-the-oracle-vm-virtualbox-product-of-oracle)
- [Oracle VM VirtualBox denial-of-service in Core](https://junglewise.ai/threats/cve-2026-87311-vulnerability-in-the-oracle-vm-virtualbox-product-of-oracle)
- [Oracle VM VirtualBox denial of service in Core](https://junglewise.ai/threats/cve-2026-87303-vulnerability-in-the-oracle-vm-virtualbox-product-of-oracle)
- [Oracle VM VirtualBox privilege escalation in Core](https://junglewise.ai/threats/cve-2026-87301-vulnerability-in-the-oracle-vm-virtualbox-product-of-oracle)
- [Oracle VM VirtualBox privilege escalation in Core component](https://junglewise.ai/threats/cve-2026-101599-vulnerability-in-the-oracle-vm-virtualbox-product-of-oracle)