In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix race between balance and cancel/pause
Syzbot reported a panic that looks like this:
assertion failed: fs_info->exclusive_operation == BTRFS_EXCLOP_BALANCE_PAUSED, in fs/btrfs/ioctl.c:465
------------[ cut here ]------------
kernel BUG at fs/btrfs/messages.c:259!
RIP: 0010:btrfs_assertfail+0x2c/0x30 fs/btrfs/messages.c:259
Call Trace:
btrfs_exclop_balance fs/btrfs/ioctl.c:465 [inline]
btrfs_ioctl_balance fs/btrfs/ioctl.c:3564 [inline]
btrfs_ioctl+0x531e/0x5b30 fs/btrfs/ioctl.c:4632
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x197/0x210 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
The reproducer is running a balance and a cancel or pause in parallel.
The way balance finishes is a bit wonky, if we were paused we need to
save the balance_ctl in the fs_info, but clear it otherwise and cleanup.
However we rely on the return values being specific errors, or having a
cancel request or no pause request. If balance completes and returns 0,
but we have a pause or cancel request we won't do the appropriate
cleanup, and then the next time we try to start a balance we'll trip
this ASSERT.
The error handling is just wrong here, we always want to clean up,
unless we got -ECANCELLED and we set the appropriate pause flag in the
exclusive op. With this patch the reproducer ran for an hour without
tripping, previously it would trip in less than a few minutes.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
- EG Severity
- Not assessed: no CVSS publishedA missing CVSS is not a severity of zero.
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-26). 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
- No SSVC decision: EchelonGraph has not assessed this CVECISA 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 BOD 26-04 block below.
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