CVE-2026-31788 — xen/privcmd: restrict usage in unprivileged domU
In the Linux kernel, the following vulnerability has been resolved: xen/privcmd: restrict usage in unprivileged domU The Xen privcmd driver allows to issue arbitrary hypercalls from user space processes. This is normally no problem, as access is usually limited to root and the hypervisor will deny any hypercalls affecting other domains. In case the guest is booted using secure boot, however, the privcmd driver would be enabling a root user process to modify e.g. kernel memory contents, thus breaking the secure boot feature. The only known case where an unprivileged domU is really needing to use the privcmd driver is the case when it is acting as the device model for another guest. In this case all hypercalls issued via the privcmd driver will target that other guest. Fortunately the privcmd driver can already be locked down to allow only hypercalls targeting a specific domain, but this mode can be activated from user land only today. The target domain can be obtained from Xenstore, so when not running in dom0 restrict the privcmd driver to that target domain from the beginning, resolving the potential problem of breaking secure boot. This is XSA-482 --- V2: - defer reading from Xenstore if Xenstore isn't ready yet (Jan Beulich) - wait in open() if target domain isn't known yet - issue message in case no target domain found (Jan Beulich)
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.2% (30-day exploitation probability)+1
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — xenbits.xen.org (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux |
version 2.6.37≥ 1c5de1939c204bde9cce87f4eb3d26e9f9eb732b and < 453b8fb68f3641fea970db88b7d9a153ed2a37e8≥ 1c5de1939c204bde9cce87f4eb3d26e9f9eb732b and < cbede2e833da1893afbea9b3ff29b5dda23a4a91≥ 1c5de1939c204bde9cce87f4eb3d26e9f9eb732b and < 389bae9a4409934e8b8d4dbdaaf02a3ae71cf8e4≥ 1c5de1939c204bde9cce87f4eb3d26e9f9eb732b and < 78432d8f0372c71c518096395537fa12be7ff24e≥ 1c5de1939c204bde9cce87f4eb3d26e9f9eb732b and < 1879319d790f7d57622cdc22807b60ea78b56b6d≥ 1c5de1939c204bde9cce87f4eb3d26e9f9eb732b and < 87a803edb2ded911cb587c53bff179d2a2ed2a28≥ 1c5de1939c204bde9cce87f4eb3d26e9f9eb732b and < 3ee5b9e3de4b8bdd74183d83205481c91a9effc8 and 1 more≥ 1c5de1939c204bde9cce87f4eb3d26e9f9eb732b and < 4eb245ff0d33b618e097a2c23de5df56d4ad6969 |
Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
version 7.0-rc5version 7.0-rc7version 7.0-rc6≥ 2.6.37.1 and < 5.10.253version 7.0-rc4version 7.0-rc3version 7.0-rc2version 7.0-rc1 and 7 moreversion 2.6.37≥ 6.19 and < 6.19.10≥ 6.13 and < 6.18.20≥ 6.7 and < 6.12.78≥ 6.2 and < 6.6.130≥ 5.16 and < 6.1.167≥ 5.11 and < 5.15.203 |
Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 8.2 | CVSS 3.1 | High | 1.5 | 6.0 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database |
| 8.2 | CVSS 3.1 | High | 1.5 | 6.0 | nvd@nist.gov via NIST National Vulnerability Database |
| 8.2 | CVSS 3.1 | High | — | — | GitHub, Inc. via GitHub Security Advisories |
| 8.2 | CVSS 3.1 | High | — | — | Linux via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H (score shown at the top: nvd@nist.gov) EPSS over time FIRST
Oct 13, 2026 → Oct 16, 2026 · 4 reading(s) · max 0.20%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
Timeline
What happened to this CVE, newest first.
- 2026
- SSVC assessment updated
- Affected products added · linux/linux
- Record published
- Fix documented
- CVSS changed · 8.2
- Source status changed · → Analyzed
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× References added · Oct 16, 2026 – Oct 16, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
16 on the record
- git.kernel.org/stable/c/cbede2e833da1893afbea9b3ff29b5dda23a4a91
- git.kernel.org/stable/c/389bae9a4409934e8b8d4dbdaaf02a3ae71cf8e4
- git.kernel.org/stable/c/87a803edb2ded911cb587c53bff179d2a2ed2a28
- git.kernel.org/stable/c/4eb245ff0d33b618e097a2c23de5df56d4ad6969
- git.kernel.org/stable/c/3ee5b9e3de4b8bdd74183d83205481c91a9effc8
- git.kernel.org/stable/c/78432d8f0372c71c518096395537fa12be7ff24e
- git.kernel.org/stable/c/1879319d790f7d57622cdc22807b60ea78b56b6d
- git.kernel.org/stable/c/453b8fb68f3641fea970db88b7d9a153ed2a37e8
- xenbits.xen.org/xsa/advisory-482.html
- github.com/advisories/GHSA-q397-v647-xvh6
- www.openwall.com/lists/oss-security/2026/03/26/4
- www.openwall.com/lists/oss-security/2026/03/24/5
- www.openwall.com/lists/oss-security/2026/03/24/3
- www.openwall.com/lists/oss-security/2026/03/24/2
- nvd.nist.gov/vuln/detail/CVE-2026-31788
- www.openwall.com/lists/oss-security/2026/03/24/4
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 1d
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 1d
- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 2d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 2d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 2d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 2d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No CWE classification.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-31788 is "xen/privcmd: restrict usage in unprivileged domU", rated High. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.2 describes technical severity. EPSS 0.20% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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