LibVNC before commit ca2a5ac02fbbadd0a21fabba779c1ea69173d10b contains heap use-after-free vulnerability in server code of file transfer extension that can result remote code execution.
Weakness
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 Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Libvncserver | Libvnc_project | * | 0.9.12 (excluding) |
| Libvncserver | Ubuntu | bionic | * |
| Libvncserver | Ubuntu | cosmic | * |
| Libvncserver | Ubuntu | esm-infra/bionic | * |
| Libvncserver | Ubuntu | esm-infra/xenial | * |
| Libvncserver | Ubuntu | trusty | * |
| Libvncserver | Ubuntu | upstream | * |
| Libvncserver | Ubuntu | xenial | * |
| X11vnc | Ubuntu | cosmic | * |
| X11vnc | Ubuntu | trusty | * |
Potential Mitigations
References
- https://ics-cert.kaspersky.com/advisories/klcert-advisories/2018/12/19/klcert-18-026-libvnc-heap-use-after-free/
- https://lists.debian.org/debian-lts-announce/2018/12/msg00017.html
- https://lists.debian.org/debian-lts-announce/2019/10/msg00042.html
- https://usn.ubuntu.com/3877-1/
- https://www.debian.org/security/2019/dsa-4383
- https://github.com/LibVNC/libvncserver/issues/241
- https://ics-cert.kaspersky.com/advisories/klcert-advisories/2018/12/19/klcert-18-026-libvnc-heap-use-after-free/
- https://lists.debian.org/debian-lts-announce/2018/12/msg00017.html
- https://lists.debian.org/debian-lts-announce/2019/10/msg00042.html
- https://usn.ubuntu.com/3877-1/
- https://www.debian.org/security/2019/dsa-4383