Description
It was discovered that websockets.c in LibVNCServer prior to 0.9.12 did not properly decode certain WebSocket frames. A malicious attacker could exploit this by sending specially crafted WebSocket frames to a server, causing a heap-based buffer overflow.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | libvncserver | 0.9.12+dfsg-3 | — |
| Debian 13 | libvncserver | 0.9.12+dfsg-3 | — |
| Debian 12 | libvncserver | 0.9.12+dfsg-3 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | veyon | No fix yet | — |
| Ubuntu 26.04 LTS | veyon | No fix yet | — |
| Ubuntu 25.10 | veyon | No fix yet | — |
| Ubuntu 24.04 LTS | veyon | No fix yet | — |
| Ubuntu 22.04 LTS | veyon | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | libvncserver | 0.9.12+dfsg-9ubuntu0.1 | USN-4407-1 |
| Ubuntu 20.04 LTS | veyon | No fix yet | — |
| Ubuntu 18.04 LTS | libvncserver | 0.9.11+dfsg-1ubuntu1.2 | USN-4407-1 |
| Ubuntu 16.04 LTS | libvncserver | 0.9.10+dfsg-3ubuntu0.16.04.4 | USN-4407-1 |
| Ubuntu 14.04 LTS | x11vnc | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | libvncserver +1 | 0.9.11-15.el8_2.1 | RHSA-2020:3385 |
| RHEL 7 | libvncserver +1 | 0.9.9-14.el7_8.1 | RHSA-2020:3281 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.1 EUS | libvncserver +1 | 0.9.11-9.el8_1.3 | RHSA-2020:3456 |
| RHEL 8.0 E4S | libvncserver | 0.9.11-9.el8_0.3 | RHSA-2020:3588 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | libvncserver-devel | 0.9.11-15.el8_2.1 | ALSA-2020:3385 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP2 | LibVNCServer | 0.9.10-4.19.1 | SUSE-SU-2020:1922-1, SUSE-SU-2020:1873-1 |
| SLES 15 SP1 | LibVNCServer | 0.9.10-4.19.1 | SUSE-SU-2020:1922-1, SUSE-SU-2020:1873-1 |
| SLES 12 SP5 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SLES 12 SP4 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SLES 12 SP3 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
Show 12 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP2 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SLES for SAP 12 SP5 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SLES for SAP 12 SP4 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SLES for SAP 12 SP3 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SLES for SAP 12 SP2 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SUSE OpenStack Cloud Crowbar 9 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SUSE OpenStack Cloud Crowbar 8 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SUSE OpenStack Cloud 9 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SUSE OpenStack Cloud 8 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SUSE OpenStack Cloud 7 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SUSE HPE Helion OpenStack 8 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
| SUSE Enterprise Storage 5 | LibVNCServer | 0.9.9-17.31.1 | SUSE-SU-2020:2167-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 15.2 | LibVNCServer | 0.9.10-lp152.9.4.1 | openSUSE-SU-2020:1056-1, openSUSE-SU-2020:1025-1, openSUSE-SU-2020:0978-1 |
| openSUSE Leap 15.1 | LibVNCServer | 0.9.10-lp151.7.6.1 | openSUSE-SU-2020:0988-1, openSUSE-SU-2020:0960-1 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | libvncserver +1 | 0.9.11-15.el8_2.1 | ELSA-2020-3385 |
| Oracle Linux 7 | libvncserver +1 | 0.9.9-14.el7_8.1 | ELSA-2020-3281 |
Advisories 18
- ALSA-2020:3385 Important: libvncserver security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2020:3456 Red Hat Security Advisory: libvncserver security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2020:3385 Red Hat Security Advisory: libvncserver security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2020:3281 Red Hat Security Advisory: libvncserver security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- USN-4407-1 libvncserver vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- openSUSE-SU-2020:0978-1 Security update for LibVNCServer SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2020:0960-1 Security update for LibVNCServer SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:1873-1 Security update for LibVNCServer SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2020:0988-1 Security update for LibVNCServer SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:2167-1 Security update for LibVNCServer SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2020:1025-1 Security update for LibVNCServer SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:1922-1 Security update for LibVNCServer SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2020:1056-1 Security update for LibVNCServer SUSE / openSUSE Security Updates · Feb 4, 2026
- RHSA-2020:3588 Red Hat Security Advisory: libvncserver security update Red Hat Security Advisories (RHSA) · Nov 22, 2025
- ICSA-21-350-12 Siemens SIMATIC ITC CISA ICS & IT advisories · May 6, 2025
- SSA-390195 SSA-390195: LibVNC Vulnerabilities in SIMATIC ITC Products Siemens ProductCERT · Dec 14, 2021
- ELSA-2020-3385 Important: libvncserver security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Aug 10, 2020
- ELSA-2020-3281 Important: libvncserver security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Aug 4, 2020
References
- https://github.com/LibVNC/libvncserver/commit/aac95a9dcf4bbba87b76c72706c3221a842ca433
- https://www.openwall.com/lists/oss-security/2020/06/30/2
- https://bugzilla.redhat.com/show_bug.cgi?id=1852356
- [oss-security] 20200630 Re: libvncserver: old websocket decoding patch mailing-list
- openSUSE-SU-2020:0960 vendor-advisory
- FEDORA-2020-37112ac660 vendor-advisory
- USN-4407-1 vendor-advisory
- FEDORA-2020-1a4b1c8271 vendor-advisory
- openSUSE-SU-2020:0978 vendor-advisory
- openSUSE-SU-2020:0988 vendor-advisory
- openSUSE-SU-2020:1025 vendor-advisory
- openSUSE-SU-2020:1056 vendor-advisory
- https://cert-portal.siemens.com/productcert/pdf/ssa-390195.pdf