CVE-2021-47491: mm: khugepaged: skip huge page collapse for special files
Vulnerability summary
CVE-2021-47491 is a medium (CVSS 5.5) vulnerability in linux. EPSS estimates a 0.21% chance of exploitation in the next 30 days, higher than 11.1% of scored vulnerabilities.
Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 8 · Related 6Timeline
- 22-05-2024PublishedVulnerability first disclosed.
- 11-05-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: mm: khugepaged: skip huge page collapse for special files The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [shy828301@gmail.com: fix vm_file check [3]]
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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.
Ubuntu86 products
- linuxAll versions (No fix recorded)
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded)
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0, < 6d67b2a73b8e3a079c355bab3c1aef7d85a044b8 | ≥ 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0, < 5fcb6fce74ffa614d964667110cf1a516c48c6d9 | ≥ 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0, < a4aeaa06d45e90f9b279f0b09de84bd00006e733 | 5.4
- linux_kernel≥ 5.4, < 5.10.78 | ≥ 5.11, < 5.14.16 | 5.15:rc1 | 5.15:rc2 | 5.15:rc3 | 5.15:rc4 | 5.15:rc5 | 5.15:rc6 | 5.15:rc7
Debian1 product
- linux< 5.15.3-1
3 vendors · 89 products
