A use-after-free flaw was found in xorg-x11-server-Xvfb. This issue occurs in Xvfb with a very specific and legacy configuration (a multi-screen setup with multiple protocol screens, also known as Zaphod mode). If the pointer is warped from a screen 1 to a screen 0, a use-after-free issue may be triggered during shutdown or reset of the Xvfb server, allowing for possible escalation of privileges or denial of service.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| X_server | X.org | 1.13.0 (including) | * |
| Red Hat Enterprise Linux 9 | RedHat | tigervnc-0:1.13.1-8.el9 | * |
| Xorg | Ubuntu | bionic | * |
| Xorg | Ubuntu | focal | * |
| Xorg | Ubuntu | lunar | * |
| Xorg | Ubuntu | mantic | * |
| Xorg | Ubuntu | oracular | * |
| Xorg | Ubuntu | trusty | * |
| Xorg | Ubuntu | xenial | * |
| Xorg-server | Ubuntu | bionic | * |
| Xorg-server | Ubuntu | focal | * |
| Xorg-server | Ubuntu | lunar | * |
| Xorg-server | Ubuntu | mantic | * |
| Xorg-server | Ubuntu | oracular | * |
| Xorg-server | Ubuntu | trusty | * |
| Xorg-server | Ubuntu | trusty/esm | * |
| Xorg-server | Ubuntu | xenial | * |
| Xorg-server-hwe-16.04 | Ubuntu | xenial | * |
| Xorg-server-hwe-18.04 | Ubuntu | bionic | * |
| Xorg-server-lts-utopic | Ubuntu | trusty | * |
| Xorg-server-lts-vivid | Ubuntu | trusty | * |
| Xorg-server-lts-wily | Ubuntu | trusty | * |
| Xorg-server-lts-xenial | Ubuntu | trusty | * |