| Name | CVE-2020-11739 |
| Description | An issue was discovered in Xen through 4.13.x, allowing guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths. The read-write unlock paths don't contain a memory barrier. On Arm, this means a processor is allowed to re-order the memory access with the preceding ones. In other words, the unlock may be seen by another processor before all the memory accesses within the "critical" section. As a consequence, it may be possible to have a writer executing a critical section at the same time as readers or another writer. In other words, many of the assumptions (e.g., a variable cannot be modified after a check) in the critical sections are not safe anymore. The read-write locks are used in hypercalls (such as grant-table ones), so a malicious guest could exploit the race. For instance, there is a small window where Xen can leak memory if XENMAPSPACE_grant_table is used concurrently. A malicious guest may be able to leak memory, or cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded. |
| Source | CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| References | DSA-4723-1 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| xen (PTS) | jessie, jessie (lts) | 4.4.4lts5-0+deb8u1 | vulnerable |
| stretch (security), stretch (lts), stretch | 4.8.5.final+shim4.10.4-1+deb9u12 | vulnerable | |
| buster (security), buster, buster (lts) | 4.11.4+107-gef32c7afa2-1 | fixed | |
| bullseye | 4.14.6-1 | fixed | |
| bullseye (security) | 4.14.5+94-ge49571868d-1 | fixed | |
| bookworm | 4.17.3+10-g091466ba55-1~deb12u1 | fixed | |
| bookworm (security) | 4.17.5+23-ga4e5191dc0-1 | fixed | |
| trixie | 4.17.3+36-g54dacb5c02-1 | fixed | |
| sid | 4.19.1-1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| xen | source | jessie | (unfixed) | end-of-life | ||
| xen | source | stretch | (unfixed) | end-of-life | ||
| xen | source | buster | 4.11.4+24-gddaaccbbab-1~deb10u1 | DSA-4723-1 | ||
| xen | source | (unstable) | 4.11.4-1 |
[stretch] - xen <end-of-life> (DSA 4602-1)
[jessie] - xen <end-of-life> (Not supported in jessie LTS)
https://xenbits.xen.org/xsa/advisory-314.html