CVE-2026-72225 jbd2: fix integer underflow in jbd2_journal_initialize_fast_commit()
An integer underflow in the Linux kernel's jbd2 journal initialization can lead to journal corruption and system abort, causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72225?
CVE-2026-72225 is a high-severity vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
jbd2: fix integer underflow in jbd2_journal_initialize_fast_commit()
jbd2_journal_initialize_fast_commit() validates journal capacity by checking (journal->j_last - num_fc_blks < JBD2_MIN_JOURNAL_BLOCKS). Both j_last and num_fc_blks are unsigned, so when num_fc_blks exceeds j_last the subtraction wraps to a large value, bypassing the bounds check.
The resulting underflow corrupts j_last, j_fc_first, and j_free, leading to journal abort.
Fix by checking num_fc_blks against j_last before the subtraction, returning -EFSCORRUPTED.
Which versions are affected by CVE-2026-72225?
How do I fix CVE-2026-72225?
Apply the vendor's patch.
Is CVE-2026-72225 being exploited?
There is no known exploitation of CVE-2026-72225 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72225, DEBIAN-CVE-2026-72225, GHSA-rm6f-75fw-gq38, UBUNTU-CVE-2026-72225.