Medium

CVE-2026-43299 — btrfs: do not ASSERT() when the fs flips RO inside btrfs_repair_io_failure()

In the Linux kernel, the following vulnerability has been resolved: btrfs: do not ASSERT() when the fs flips RO inside btrfs_repair_io_failure() [BUG] There is a bug report that when btrfs hits ENOSPC error in a critical path, btrfs flips RO (this part is expected, although the ENOSPC bug still needs to be addressed). The problem is after the RO flip, if there is a read repair pending, we can hit the ASSERT() inside btrfs_repair_io_failure() like the following: BTRFS info (device vdc): relocating block group 30408704 flags metadata|raid1 ------------[ cut here ]------------ BTRFS: Transaction aborted (error -28) WARNING: fs/btrfs/extent-tree.c:3235 at __btrfs_free_extent.isra.0+0x453/0xfd0, CPU#1: btrfs/383844 Modules linked in: kvm_intel kvm irqbypass [...] ---[ end trace 0000000000000000 ]--- BTRFS info (device vdc state EA): 2 enospc errors during balance BTRFS info (device vdc state EA): balance: ended with status: -30 BTRFS error (device vdc state EA): parent transid verify failed on logical 30556160 mirror 2 wanted 8 found 6 BTRFS error (device vdc state EA): bdev /dev/nvme0n1 errs: wr 0, rd 0, flush 0, corrupt 10, gen 0 [...] assertion failed: !(fs_info->sb->s_flags & SB_RDONLY) :: 0, in fs/btrfs/bio.c:938 ------------[ cut here ]------------ assertion failed: !(fs_info->sb->s_flags & SB_RDONLY) :: 0, in fs/btrfs/bio.c:938 kernel BUG at fs/btrfs/bio.c:938! Oops: invalid opcode: 0000 [#1] SMP NOPTI CPU: 0 UID: 0 PID: 868 Comm: kworker/u8:13 Tainted: G W N 6.19.0-rc6+ #4788 PREEMPT(full) Tainted: [W]=WARN, [N]=TEST Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 Workqueue: btrfs-endio simple_end_io_work RIP: 0010:btrfs_repair_io_failure.cold+0xb2/0x120 RSP: 0000:ffffc90001d2bcf0 EFLAGS: 00010246 RAX: 0000000000000051 RBX: 0000000000001000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff8305cf42 RDI: 00000000ffffffff RBP: 0000000000000002 R08: 00000000fffeffff R09: ffffffff837fa988 R10: ffffffff8327a9e0 R11: 6f69747265737361 R12: ffff88813018d310 R13: ffff888168b8a000 R14: ffffc90001d2bd90 R15: ffff88810a169000 FS: 0000000000000000(0000) GS:ffff8885e752c000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 ------------[ cut here ]------------ [CAUSE] The cause of -ENOSPC error during the test case btrfs/124 is still unknown, although it's known that we still have cases where metadata can be over-committed but can not be fulfilled correctly, thus if we hit such ENOSPC error inside a critical path, we have no choice but abort the current transaction. This will mark the fs read-only. The problem is inside the btrfs_repair_io_failure() path that we require the fs not to be mount read-only. This is normally fine, but if we are doing a read-repair meanwhile the fs flips RO due to a critical error, we can enter btrfs_repair_io_failure() with super block set to read-only, thus triggering the above crash. [FIX] Just replace the ASSERT() with a proper return if the fs is already read-only.

Published May 8, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.1% (30-day exploitation probability)+0
Technical severity (medium)+3

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.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.12%

ahead of 2% of scored CVEs · Oct 14, 2026

Affects

Linux

Linux and 1 more

CVSS base

5.5

Medium · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)

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, Linux Linux Kernel).
Apply the fixed version or the patch documented under Remediation.
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	≥ 908960c6c0fb3b3ce3971dc0ca47b581d256b968 and < f6df18c001e3dcebc08482d0adeacd0cfea08593≥ 908960c6c0fb3b3ce3971dc0ca47b581d256b968 and < 8ceaad6cd6e7fa5f73b0b2796a2e85d75d37e9f3version 3.13≥ 908960c6c0fb3b3ce3971dc0ca47b581d256b968 and < 81e1ae665004b99a10686473d99f0a7cb6335f38	Vulnerable	CVE Program (cve.org) e CISA ADP
Linux	Linux Kernel	≥ 3.13 and < 6.19.6	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.5	CVSS 3.1	Medium	1.8	3.6	nvd@nist.gov via NIST National Vulnerability Database
5.5	CVSS 3.1	Medium	—	—	GitHub, Inc. via GitHub Security Advisories

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.12%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.

endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · Analyzed → Modified
Oct 15, 2026 · NIST National Vulnerability Database
Affected products added · linux/linux
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 5.5
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
May 8, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

2× References added · Oct 15, 2026 – Oct 15, 2026
1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

5 on the record

git.kernel.org/stable/c/8ceaad6cd6e7fa5f73b0b2796a2e85d75d37e9f3
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/f6df18c001e3dcebc08482d0adeacd0cfea08593
Patch, NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2026-43299
GitHub Security Advisories
git.kernel.org/stable/c/81e1ae665004b99a10686473d99f0a7cb6335f38
NIST National Vulnerability Database
github.com/advisories/GHSA-v7w4-33p2-qjcr
GitHub Security Advisories

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 7h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 7h
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d

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 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-2026-43299 is "btrfs: do not ASSERT() when the fs flips RO inside btrfs_repair_io_failure()", rated Medium. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.5 describes technical severity. EPSS 0.12% 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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