CVE-2021-47004

CVE-2021-47004 is a high-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 7.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid touching checkpointed data in get_victim() In CP disabling mode, there are two issues when using LFS or SSR | AT_SSR mode to select victim: 1. LFS is set to find source section during GC, the victim should have no checkpointed data, since after GC, section could not be set free for reuse. Previously, we only check valid chpt blocks in current segment rather than section, fix it. 2. SSR | AT_SSR are set to find target segment for writes which can be fully filled by checkpointed and newly written blocks, we should never select such segment, otherwise it can cause panic or data corruption during allocation, potential case is described as below: a) target segment has 'n' (n < 512) ckpt valid blocks b) GC migrates 'n' valid blocks to other segment (segment is still in dirty list) c) GC migrates '512 - n' blocks to target segment (segment has 'n' cp_vblocks and '512 - n' vblocks) d) If GC selects target segment via {AT,}SSR allocator, however there is no free space in targe segment.

Frequently asked questions

What is CVE-2021-47004?
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid touching checkpointed data in get_victim() In CP disabling mode, there are two issues when using LFS or SSR | AT_SSR mode to select victim: 1. LFS is set to find source section during GC, the victim should have no checkpointed data, since after GC, section could not be set free for reuse. Previously, we only check valid chpt blocks in current segment rather than section, fix it. 2. SSR | AT_SSR are set to find target segment for writes which can be fully filled by checkpointed and newly written blocks, we should never select such segment, otherwise it can cause panic or data corruption during allocation, potential case is described as below: a) target segment has 'n' (n < 512) ckpt valid blocks b) GC migrates 'n' valid blocks to other segment (segment is still in dirty list) c) GC migrates '512 - n' blocks to target segment (segment has 'n' cp_vblocks and '512 - n' vblocks) d) If GC selects target segment via {AT,}SSR allocator, however there is no free space in targe segment.
How severe is CVE-2021-47004?
CVE-2021-47004 has a CVSS 3.x base score of 7.1, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability high.
Is CVE-2021-47004 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (15th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-47004?
CVE-2021-47004 affects Linux Linux Kernel. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-47004?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2021-47004 have an EU (EUVD) identifier?
Yes. CVE-2021-47004 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-33652.
When was CVE-2021-47004 published?
CVE-2021-47004 was published on 2024-02-28 and last updated on 2026-06-17.

References

Affected products (1)

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