CVE-2026-31450
Description
A race was found in ext4: ext4_inode_attach_jinode() published ei->jinode before jbd2_journal_init_jbd_inode() finished initializing it, so concurrent readers could observe a non-NULL journal inode whose i_vfs_inode was still NULL. The fast-commit flush path then called jbd2_wait_inode_data() and faulted on i_mapping. Upstream publishes the pointer only after full initialization using WRITE_ONCE/READ_ONCE and a write memory barrier.
Statement
Red Hat acknowledges this ext4 fast-commit lifecycle bug as fixed upstream. Impact is a local crash/Denial-of-Service class defect reachable through fdatasync-heavy workloads with fast commit enabled. Supported products receive the fix through rebased kernels. Treat as kernel stability until product security completes exploitability review.
Mitigation
To mitigate this issue, prevent the ext4 module from being loaded. See https://access.redhat.com/solutions/41278 for instructions.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | N/A | 8.8 |
| Attack Vector | Local | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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