CVE-2021-47255: kvm: LAPIC: Restore guard to prevent illegal APIC register access
Vulnerability summary
CVE-2021-47255 is a high (CVSS 7.1) vulnerability in linux. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 15.6% of scored vulnerabilities.
Not severe (CVSS 7.1, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 4 · Related 4Timeline
- 21-05-2024PublishedVulnerability first disclosed.
- 11-05-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: kvm: LAPIC: Restore guard to prevent illegal APIC register access Per the SDM, "any access that touches bytes 4 through 15 of an APIC register may cause undefined behavior and must not be executed." Worse, such an access in kvm_lapic_reg_read can result in a leak of kernel stack contents. Prior to commit 01402cf81051 ("kvm: LAPIC: write down valid APIC registers"), such an access was explicitly disallowed. Restore the guard that was removed in that commit.
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated7.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
EPSS trend
Probability
0.24%
Chance of exploitation in the next 30 days
Percentile
16%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.24% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeNo weakness data has been published for this record.
Affected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu82 products
- linux< 5.4.0-81.91
- linux-allwinner-5.19All versions (No fix recorded)
- linux-aws< 5.4.0-1055.58
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 01402cf81051f796dac7c60ca11d6147153ca46a, < bf99ea52970caeb4583bdba1192c1f9b53b12c84 | ≥ 01402cf81051f796dac7c60ca11d6147153ca46a, < 018685461a5b9a9a70e664ac77aef0d7415a3fd5 | ≥ 01402cf81051f796dac7c60ca11d6147153ca46a, < a2aff09807fbe4018c269d3773a629949058b210 | ≥ 01402cf81051f796dac7c60ca11d6147153ca46a, < 218bf772bddd221489c38dde6ef8e917131161f6 | 5.3
- linux_kernel≥ 5.3, < 5.4.128 | ≥ 5.5, < 5.10.46 | ≥ 5.11, < 5.12.13 | 5.13:rc1 | 5.13:rc2 | 5.13:rc3 | 5.13:rc4 | 5.13:rc5 | 5.13:rc6
Debian1 product
- linux< 5.10.46-1
3 vendors · 85 products
