CVE-2026-23238
Description
In 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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
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OS impact
Linux kernel Affected 3 releases
| Version | Status | Fixed in |
|---|---|---|
| 6.19 | Affected | — |
| 2.6.12 | Affected | — |
| — | Affected | 5.10.251 |
SUSE Affected 1 release
| Version | Status | Fixed in |
|---|---|---|
| — | Affected | — |
Debian Fixed 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Fixed | 6.12.74-2 |
| sid | Fixed | 6.18.13-1 |
| forky | Fixed | 6.18.13-1 |
| bullseye | Fixed | 5.10.251-1 |
| bookworm | Fixed | 6.1.164-1 |
References
- https://www.suse.com/security/cve/CVE-2026-23238.html
- https://security-tracker.debian.org/tracker/CVE-2026-23238
- https://git.kernel.org/stable/c/2c5829cd8fbbc91568c520b666898f57cdcb8cf6
- https://git.kernel.org/stable/c/4b71ad7676564a94ec5f7d18298f51e8ae53db73
- https://git.kernel.org/stable/c/9b203b8ddd7359270e8a694d0584743555128e2c
- https://git.kernel.org/stable/c/a381f0f61b35c8894b0bd0d6acef2d8f9b08b244
- https://git.kernel.org/stable/c/ab7ad7abb3660c58ffffdf07ff3bb976e7e0afa0
- https://git.kernel.org/stable/c/cbd9931e6456822067725354d83446c5bb813030
- https://git.kernel.org/stable/c/f2521ab1f63a8c244f06a080319e5ff9a2e1bd95
- https://cert-portal.siemens.com/productcert/html/ssa-253495.html
CWEs
CWE-617
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.