CVE-2021-47450: KVM: arm64: Fix host stage-2 PGD refcount
Vulnerability summary
CVE-2021-47450 is a high (CVSS 8.8) vulnerability in linux. EPSS estimates a 0.21% chance of exploitation in the next 30 days, higher than 10.9% of scored vulnerabilities.
Not severe (CVSS 8.8, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 5 · Related 5Timeline
- 22-05-2024PublishedVulnerability first disclosed.
- 05-08-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Fix host stage-2 PGD refcount The KVM page-table library refcounts the pages of concatenated stage-2 PGDs individually. However, when running KVM in protected mode, the host's stage-2 PGD is currently managed by EL2 as a single high-order compound page, which can cause the refcount of the tail pages to reach 0 when they shouldn't, hence corrupting the page-table. Fix this by introducing a new hyp_split_page() helper in the EL2 page allocator (matching the kernel's split_page() function), and make use of it from host_s2_zalloc_pages_exact().
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated8.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HDiffers
- NVDNIST5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HDiffers
EPSS trend
Probability
0.21%
Chance of exploitation in the next 30 days
Percentile
11%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.21% 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.
Ubuntu62 products
- linux-allwinner-5.19All versions (No fix recorded)
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
- linux-aws-5.13All versions (No fix recorded)
- linux-aws-5.19All versions (No fix recorded)
Linux2 products
- linux≥ 1025c8c0c6accfcbdc8f52ca1940160f65cd87d6, < b372264c66ef78f2cab44e877fbd765ad6d24c39 | ≥ 1025c8c0c6accfcbdc8f52ca1940160f65cd87d6, < 1d58a17ef54599506d44c45ac95be27273a4d2b1 | 5.13
- linux_kernel≥ 5.13, < 5.14.15 | 5.15:rc1 | 5.15:rc2 | 5.15:rc3 | 5.15:rc4 | 5.15:rc5 | 5.15:rc6
Debian1 product
- linux< 5.15.3-1
3 vendors · 65 products
