CVE-2026-90261
Low risk· EPSS 10%Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
In the Linux kernel, the btrfs filesystem on zoned devices has a bug that intermittently aborts transactions and forces the filesystem read-only. The issue occurs during metadata-heavy relocation when btree_writepages() encounters an active block group at a higher logical address, leading to -EAGAIN and transaction abort. The fix flushes active metadata and system block groups at the start of btree_writepages() to avoid deadlock and ensure forward progress.
Risk Assessment
The risk is that the btrfs filesystem may suddenly become read-only, causing data unavailability and service interruptions. The bug is intermittent, especially during relocation operations, making it hard to predict and potentially leading to availability issues.
Recommendation
It is recommended to update the Linux kernel to a version containing the fix for CVE-2026-90261 as soon as possible. Before updating, avoid intensive relocation operations on btrfs with zoned devices if possible.
Other vulnerabilities in Linux kernel
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- CVE-2026-99258Unknown
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- CVE-2026-99257Unknown
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- CVE-2026-99251Unknown
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- CVE-2026-99250Unknown
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In the Linux kernel, zap_pid_ns_processes() waiting for PID namespace cleanup was not freezable. A tracer outside the namespace that does not reap its traced zombies keeps PIDs allocated, making the wait unbounded and causing every suspend attempt to fail. The fix makes the wait loops use TASK_FREEZABLE states so the freezer can freeze waiting tasks.
- CVE-2026-99248Unknown
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- CVE-2026-99247Unknown
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

