In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to avoid accessing uninitialized curseg
syzbot reports a f2fs bug as below:
F2FS-fs (loop3): Stopped filesystem due to reason: 7
kworker/u8:7: attempt to access beyond end of device
BUG: unable to handle page fault for address: ffffed1604ea3dfa
RIP: 0010:get_ckpt_valid_blocks fs/f2fs/segment.h:361 [inline]
RIP: 0010:has_curseg_enough_space fs/f2fs/segment.h:570 [inline]
RIP: 0010:__get_secs_required fs/f2fs/segment.h:620 [inline]
RIP: 0010:has_not_enough_free_secs fs/f2fs/segment.h:633 [inline]
RIP: 0010:has_enough_free_secs+0x575/0x1660 fs/f2fs/segment.h:649
f2fs_is_checkpoint_ready fs/f2fs/segment.h:671 [inline]
f2fs_write_inode+0x425/0x540 fs/f2fs/inode.c:791
write_inode fs/fs-writeback.c:1525 [inline]
__writeback_single_inode+0x708/0x10d0 fs/fs-writeback.c:1745
writeback_sb_inodes+0x820/0x1360 fs/fs-writeback.c:1976
wb_writeback+0x413/0xb80 fs/fs-writeback.c:2156
wb_do_writeback fs/fs-writeback.c:2303 [inline]
wb_workfn+0x410/0x1080 fs/fs-writeback.c:2343
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
worker_thread+0x870/0xd30 kernel/workqueue.c:3398
kthread+0x7a9/0x920 kernel/kthread.c:464
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Commit 8b10d3653735 ("f2fs: introduce FAULT_NO_SEGMENT") allows to trigger
no free segment fault in allocator, then it will update curseg->segno to
NULL_SEGNO, though, CP_ERROR_FLAG has been set, f2fs_write_inode() missed
to check the flag, and access invalid curseg->segno directly in below call
path, then resulting in panic:
- f2fs_write_inode
- f2fs_is_checkpoint_ready
- has_enough_free_secs
- has_not_enough_free_secs
- __get_secs_required
- has_curseg_enough_space
- get_ckpt_valid_blocks
: access invalid curseg->segno
To avoid this issue, let's:
- check CP_ERROR_FLAG flag in prior to f2fs_is_checkpoint_ready() in
f2fs_write_inode().
- in has_curseg_enough_space(), save curseg->segno into a temp variable,
and verify its validation before use.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it