CVE-2026-89493: In the Linux kernel, the following vulnerability has been resolved: ocfs2: validate rl_used against rl_count in refcount block validator ocfs2_find_refcount

In the Linux kernel, the following vulnerability has been resolved: ocfs2: validate rl_used against rl_count in refcount block validator ocfs2_find_refcount_r

In the Linux kernel, the following vulnerability has been resolved: ocfs2: validate rl_used against rl_count in refcount block validator ocfs2_find_refcount_rec_in_rl() walks the on-disk refcount record array with: for (; i < le16_to_cpu(rb->rf_records.rl_used); i++) { rec = &rb->rf_records.rl_recs[i]; ... rl_recs[] lives in a single metadata block (4096 bytes on the common configuration), so its real capacity is fixed by ocfs2_refcount_recs_per_rb(sb) (247 records for a 4K block with the 16-byte ocfs2_refcount_rec). rl_used and rl_count are both read directly off disk by ocfs2_validate_refcount_block() and are never checked against that capacity, nor against each other, before any refcount/reflink/CoW operation walks the array. A crafted (or corrupted) refcount block with rl_used == 0xffff makes the loop above walk far past the end of the block, dereferencing rl_recs[i] for i up to 65534. The resulting index is then handed to the sibling ocfs2_insert_refcount_rec(), whose insert-shift does: if (index < le16_to_cpu(rf_list->rl_used)) memmove(&rf_list->rl_recs[index + 1], &rf_list->rl_recs[index], (le16_to_cpu(rf_list->rl_used) - index) * sizeof(struct ocfs

Description from the National Vulnerability Database, published by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

What it means for a small business

Linux is on the computers, phones or browsers your team uses every day. Turn on automatic updates and restart: most of these fixes only take effect after a restart.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.65%, higher than 51% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 29, 2026, updated daily.

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Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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