Linux KernelOperating system · Linux
CVE-2026-23238
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn the Linux kernel, the following vulnerability has been resolved: romfs: check sb_set_blocksize() return value romfs_fill_super() ignores the return value of sb_set_blocksize(), which can fail if the requested block size is incompatible with the block device's configuration. This can be triggered by setting a loop device's block size larger than PAGE_SIZE using ioctl(LOOP_SET_BLOCK_SIZE, 32768), then mounting a romfs filesystem on that device. When sb_set_blocksize(sb, ROMBSIZE) is called with ROMBSIZE=4096 but the device has logical_block_size=32768, bdev_validate_blocksize() fails because the requested size is smaller than the device's logical block size. sb_set_blocksize() returns 0 (failure), but romfs ignores this and continues mounting. The superblock's block size remains at the device's logical block size (32768). Later, when sb_bread() attempts I/O with this oversized block size, it triggers a kernel BUG in folio_set_bh(): kernel BUG at fs/buffer.c:1582! BUG_ON(size > PAGE_SIZE); Fix by checking the return value of sb_set_blocksize() and failing the mount with -EINVAL if it returns 0.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysisAttacker-controllable input can reach an assertion that aborts the process when it fails, so a check meant for debugging becomes a denial-of-service in production. A single crafted request takes the service down. The fix is to handle unexpected input gracefully on reachable paths rather than asserting on it.
General guidance for the reachable assertion class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Linux KernelOperating system
>= 2.6.12.1, < 5.10.251>= 5.11, < 5.15.201>= 5.16, < 6.1.164>= 6.2, < 6.6.127>= 6.7, < 6.12.74>= 6.13, < 6.18.13= 2.6.12= 6.19CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped5.10.2515.15.2016.1.164
Upgrade to kernel >=5.10.251 (5.10.x), >=5.15.201 (5.11-5.14), >=6.1.164 (5.16-6.0), or >=6.6.127 (6.2-6.6) depending on your current branch
- Identify the currently running kernel version using `uname -r`
- Determine which affected version range your kernel falls into based on the CVSS advisory
- Upgrade to a patched kernel version: for 5.10.x line upgrade to >=5.10.251, for 5.11-5.14 upgrade to >=5.15.201, for 5.16-6.0 upgrade to >=6.1.164, for 6.2-6.6 upgrade to >=6.6.127
- Use your distribution's package manager to install the new kernel (e.g., `apt update && apt install linux-image-*` for Debian/Ubuntu, `yum update kernel` for RHEL/CentOS, or `pacman -Syu linux` for Arch)
- Reboot the system to load the patched kernel: `sudo reboot`
- Verify the new kernel is running with `uname -r`
- As a temporary mitigation, avoid mounting romfs filesystems on loop devices with block sizes larger than PAGE_SIZE (4096)
Generated from the published advisory — verify against the referenced sources before acting.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-23238 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-23238 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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