Description
An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to cause a denial of service via a VCPUOP_initialise hypercall. hypercall_create_continuation() is a variadic function which uses a printf-like format string to interpret its parameters. Error handling for a bad format character was done using BUG(), which crashes Xen. One path, via the VCPUOP_initialise hypercall, has a bad format character. The BUG() can be hit if VCPUOP_initialise executes for a sufficiently long period of time for a continuation to be created. Malicious guests may cause a hypervisor crash, resulting in a Denial of Service (DoS). Xen versions 4.6 and newer are vulnerable. Xen versions 4.5 and earlier are not vulnerable. Only x86 PV guests can exploit the vulnerability. HVM and PVH guests, and guests on ARM systems, cannot exploit the vulnerability.
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 | xen | 4.11.3+24-g14b62ab3e5-1 | — |
| Debian 13 | xen | 4.11.3+24-g14b62ab3e5-1 | — |
| Debian 12 | xen | 4.11.3+24-g14b62ab3e5-1 | — |
| Debian 10 | xen | 4.11.3+24-g14b62ab3e5-1~deb10u1 | DSA-4602-1 |
| Debian 9 | xen | 4.8.5.final+shim4.10.4-1+deb9u12 | DSA-4602-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | xen | No fix yet | — |
| Ubuntu 16.04 LTS | xen | No fix yet | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP1 | xen | 4.12.1_04-3.6.1 | SUSE-SU-2019:2961-1 |
| SLES 15 | xen | 4.10.4_06-3.25.1 | SUSE-SU-2019:2960-1 |
| SLES 12 SP4 | xen | 4.11.2_04-2.17.1 | SUSE-SU-2019:2962-1 |
| SLES 12 SP3 | xen | 4.9.4_06-3.59.1 | SUSE-SU-2019:3297-1 |
| SLES 12 SP2 | xen | 4.7.6_06-43.59.1 | SUSE-SU-2020:0334-1 |
Show 11 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP1 | xen | 4.5.5_28-22.64.1 | SUSE-SU-2020:0388-1 |
| SLES 11 SP4 | xen | 4.4.4_42-61.52.1 | SUSE-SU-2020:14444-1 |
| SLES for SAP 12 SP4 | xen | 4.11.2_04-2.17.1 | SUSE-SU-2019:2962-1 |
| SLES for SAP 12 SP3 | xen | 4.9.4_06-3.59.1 | SUSE-SU-2019:3297-1 |
| SLES for SAP 12 SP2 | xen | 4.7.6_06-43.59.1 | SUSE-SU-2020:0334-1 |
| SLES for SAP 12 SP1 | xen | 4.5.5_28-22.64.1 | SUSE-SU-2020:0388-1 |
| SUSE OpenStack Cloud Crowbar 8 | xen | 4.9.4_06-3.59.1 | SUSE-SU-2019:3297-1 |
| SUSE OpenStack Cloud 8 | xen | 4.9.4_06-3.59.1 | SUSE-SU-2019:3297-1 |
| SUSE OpenStack Cloud 7 | xen | 4.7.6_06-43.59.1 | SUSE-SU-2020:0334-1 |
| SUSE HPE Helion OpenStack 8 | xen | 4.9.4_06-3.59.1 | SUSE-SU-2019:3297-1 |
| SUSE Enterprise Storage 5 | xen | 4.9.4_06-3.59.1 | SUSE-SU-2019:3297-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 15.0 | xen | 4.10.4_06-lp150.2.25.1 | openSUSE-SU-2019:2506-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.9 | xen | 4.11.2-r0 | — |
Advisories 9
- DSA-4602-1 xen - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2019:2960-1 Security update for xen SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:0334-1 Security update for xen SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2019:2962-1 Security update for xen SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:14444-1 Security update for xen SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2019:2961-1 Security update for xen SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2019:2506-1 Security update for xen SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2019:3297-1 Security update for xen SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2020:0388-1 Security update for xen SUSE / openSUSE Security Updates · Feb 4, 2026
References
- http://xenbits.xen.org/xsa/advisory-296.html
- [oss-security] 20191031 Xen Security Advisory 296 v4 (CVE-2019-18420) - VCPUOP_initialise DoS mailing-list
- openSUSE-SU-2019:2506 vendor-advisory
- FEDORA-2019-865bb16900 vendor-advisory
- FEDORA-2019-376ec5c107 vendor-advisory
- FEDORA-2019-cbb732f760 vendor-advisory
- DSA-4602 vendor-advisory
- 20200114 [SECURITY] [DSA 4602-1] xen security update mailing-list
- GLSA-202003-56 vendor-advisory