CVE-2026-90261 — btrfs: zoned: flush active metadata block group at btree_writepages() start
In the Linux kernel, the following vulnerability has been resolved: btrfs: zoned: flush active metadata block group at btree_writepages() start btree_writepages() writes the btree inode's dirty metadata in ascending logical address order. On a zoned filesystem only one metadata and one system block group is active for writing at a time, and check_bg_is_active() (via btrfs_check_meta_write_pointer()) pivots the active block group as writeback moves from one block group to the next. If the active block group sits at a higher logical address than another block group that also holds dirty metadata, the ascending walk reaches the lower one first and, to write it, has to finish the active block group and activate the lower one. It cannot finish a block group that still has unsent IO, and during WB_SYNC_ALL && !for_sync (commit) writeback it deliberately refuses to wait for that IO under fs_info->zoned_meta_io_lock, as that can deadlock. The pivot thus cannot issue the submission itself either, so it gives up: btrfs_check_meta_write_pointer() returns -EAGAIN, which btrfs_write_and_wait_transaction() treats as fatal and aborts the transaction, forcing the filesystem read-only. This happens intermittently under metadata-heavy relocation (e.g. fstests btrfs/187). Flush the active metadata and system block groups at the start of btree_writepages(), under the fs_info->zoned_meta_io_lock it already holds, so they have no unsent IO left and the later pivot can finish them and make forward progress.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.2% (30-day exploitation probability)+2
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux | ≥ 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 and < 58b0ab0340ce04a057169d42cbacbf786063813d≥ 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 and < e2de2989adb3e58c2320e57c255f52e065667b5e≥ 13bb483d32abb6f8ebd40141d87eb68f11cc2dd2 and < ecc05eda9a346848ae01a6c8bfa3f0bec133bd8bversion fca3a1cd3ba47f1815e0c0fcdc9aafaf02ee0a75≥ 6.5.5 and < 6.6version 6.6 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Not enough vector or weakness data: use the affected application’s logs as a starting point.
Timeline
What happened to this CVE, newest first.
- 2026
- Record published
- Affected products added · linux/linux
- Source status changed · → Received
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 15, 2026 – Oct 15, 2026
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
5 on the record
Elsewhere on this site
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- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
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- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
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Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No CVSS score published by NVD, the CNA, CISA or GitHub so far.
- No fixed version, patch or mitigation documented.
- No CISA SSVC assessment.
- No CWE classification.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-90261 is "btrfs: zoned: flush active metadata block group at btree_writepages() start", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.22% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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