CVE-2026-72225

jbd2: fix integer underflow in jbd2_journal_initialize_fast_commit()

Published Aug 15, 2026 CVSS 3.1 · 7.8 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Ubuntu USN Ubuntu USN USN-8876-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8875-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8877-1 Linux kernel (GCP) vulnerabilities
Ubuntu USN Ubuntu USN USN-8878-1 Linux kernel (GCP) vulnerabilities
Ubuntu USN Ubuntu USN USN-8879-1 Linux kernel (Oracle) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8888-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8889-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-2 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8888-2 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8875-2 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8917-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8918-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9003-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9029-1 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9043-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Weaknesses CWE-189
Type Values Removed Values Added
Weaknesses CWE-189
Type Values Removed Values Added
Weaknesses CWE-190
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-190
Type Values Removed Values Added
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.
Title jbd2: fix integer underflow in jbd2_journal_initialize_fast_commit()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 16, 2026, 6:45 PM
Reserved
Aug 9, 2026, 3:40 AM
Status
Received
Published
Aug 15, 2026, 6:21 AM
Modified
Oct 16, 2026, 7:17 PM
Severity
Low
Public date
Aug 15, 2026, 12:00 AM