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CVE Record

CVE-2025-38218: f2fs: fix to do sanity check on sit_bitmap_size

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to do sanity check on sit_bitmap_size w/ below testcase, resize will generate a corrupted image which contains inconsistent metadata, so when mounting such image, it will trigger kernel panic: touch img truncate -s $((512*1024*1024*1024)) img mkfs.f2fs -f img $((256*1024*1024)) resize.f2fs -s -i img -t $((1024*1024*1024)) mount img /mnt/f2fs ------------[ cut here ]------------ kernel BUG at fs/f2fs/segment.h:863! Oops: invalid opcode: 0000 [#1] SMP PTI CPU: 11 UID: 0 PID: 3922 Comm: mount Not tainted 6.15.0-rc1+ #191 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:f2fs_ra_meta_pages+0x47c/0x490 Call Trace: f2fs_build_segment_manager+0x11c3/0x2600 f2fs_fill_super+0xe97/0x2840 mount_bdev+0xf4/0x140 legacy_get_tree+0x2b/0x50 vfs_get_tree+0x29/0xd0 path_mount+0x487/0xaf0 __x64_sys_mount+0x116/0x150 do_syscall_64+0x82/0x190 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7fdbfde1bcfe The reaseon is: sit_i->bitmap_size is 192, so size of sit bitmap is 192*8=1536, at maximum there are 1536 sit blocks, however MAIN_SEGS is 261893, so that sit_blk_cnt is 4762, build_sit_entries() -> current_sit_addr() tries to access out-of-boundary in sit_bitmap at offset from [1536, 4762), once sit_bitmap and sit_bitmap_mirror is not the same, it will trigger f2fs_bug_on(). Let's add sanity check in f2fs_sanity_check_ckpt() to avoid panic.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A malformed F2FS filesystem image can crash a vulnerable Linux kernel when mounted. The issue threatens hosts that use F2FS or process untrusted filesystem images. The supplied evidence demonstrates a kernel panic; it does not establish real-world data theft, modification, or active exploitation.

Executive priority

Prioritize patching systems that mount F2FS media or filesystem images, especially multi-user, removable-media, and image-processing environments. Treat this primarily as a host-crash risk based on available evidence. Validate distribution fixes rather than relying solely on upstream version numbers.

Technical view

F2FS trusted an inconsistent sit_bitmap_size during checkpoint validation. The reported image advertised bitmap capacity for 1,536 SIT blocks while metadata required 4,762, causing an out-of-bounds bitmap access and f2fs_bug_on() kernel panic. The kernel fix adds a sanity check in f2fs_sanity_check_ckpt() to reject inconsistent metadata.

Likely exposure

Exposure is most likely where affected Linux kernels mount malformed or attacker-influenced F2FS filesystems. Systems not using F2FS have lower practical exposure. The bundled version data spans multiple stable kernel lines but is insufficiently structured to determine every distribution-specific vulnerable or fixed package.

Exploitation context

The CVSS 3.1 score is 7.8 with local access, low complexity, low privileges, and no user interaction. The supplied record is not in KEV and provides no evidence of active exploitation. It documents a reproducible kernel panic involving a corrupted filesystem image.

Researcher notes

The demonstrated mismatch permits current_sit_addr() to index beyond the SIT bitmap before a mirror comparison triggers f2fs_bug_on(). Although the CVSS vector assigns high confidentiality, integrity, and availability impacts, the supplied narrative directly demonstrates only a panic. No CWE classification or public exploitation evidence is provided.

Mitigation direction

  • Install a vendor kernel containing the applicable stable F2FS sanity-check fix.
  • Check distribution advisories for the fixed package corresponding to each deployed kernel line.
  • Restrict mounting of untrusted or externally supplied F2FS images until systems are patched.
  • Reduce unnecessary F2FS support or usage where operationally feasible.

Validation and detection

  • Inventory Linux kernel versions and identify systems using or capable of mounting F2FS.
  • Confirm vendor packages include the referenced sit_bitmap_size sanity-check backport.
  • Review kernel logs for F2FS mount failures, f2fs_build_segment_manager traces, or kernel BUG events.
  • Validate malformed F2FS metadata is rejected safely in an isolated, non-production environment.
Prepared
Confidence
medium
Sources
11

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2025-38218 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
1ADP providers
10Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-38218Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux98e4da8ca301e062d79ae168c67e56f3c3de3ce4, 98e4da8ca301e062d79ae168c67e56f3c3de3ce4, 98e4da8ca301e062d79ae168c67e56f3c3de3ce4, 98e4da8ca301e062d79ae168c67e56f3c3de3ce4, 98e4da8ca301e062d79ae168c67e56f3c3de3ce4, 98e4da8ca301e062d79ae168c67e56f3c3de3ce4, 98e4da8ca301e062d79ae168c67e56f3c3de3ce4unaffected
LinuxLinux3.8, 0, 5.10.239, 5.15.186, 6.1.142, 6.6.95, 6.12.35, 6.15.4, 6.16affected
Weakness

CWE details

No CWE listed

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