In the Linux kernel, the following vulnerability has been resolved:
ext4: fix off-by-one errors in fast-commit block filling
Due to several different off-by-one errors, or perhaps due to a late change in design that wasn't fully reflected in the code that was actually merged, there are several very strange constraints on how fast-commit blocks are filled with tlv entries:
- tlvs must start at least 10 bytes before the end of the block, even though the minimum tlv length is 8. Otherwise, the replay code will ignore them. (BUG: ext4_fc_reserve_space() could violate this requirement if called with a len of blocksize - 9 or blocksize - 8. Fortunately, this doesn't seem to happen currently.)
- tlvs must end at least 1 byte before the end of the block. Otherwise the replay code will consider them to be invalid. This quirk contributed to a bug (fixed by an earlier commit) where uninitialized memory was being leaked to disk in the last byte of blocks.
Also, strangely these constraints don't apply to the replay code in e2fsprogs, which will accept any tlvs in the blocks (with no bounds checks at all, but that is a separate issue...).
Given that this all seems to be a bug, let's fix it by just filling blocks with tlv entries in the natural way.
Note that old kernels will be unable to replay fast-commit journals created by kernels that have this commit.
CVSS Details
- CVSS 3.1 Base Score: 5.5
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade python-perf-debuginfoUpgrade kernel-headersUpgrade kernel-tools-debuginfoUpgrade kernel-debuginfoUpgrade perf-debuginfoUpgrade perfUpgrade kernel-tools-develUpgrade kernel-debuginfo-common-aarch64Upgrade kernelUpgrade kernel-develUpgrade bpftoolUpgrade kernel-livepatch-5.15.90-54.138Upgrade kernel-debuginfo-common-x86_64Upgrade python-perfUpgrade bpftool-debuginfoUpgrade kernel-tools | May 20, 2026 | May 20, 2026 |
| Debian | — | Upgrade linux | Oct 3, 2025 | Oct 3, 2025 |
| Huawei Euleros 2_0_sp11 | — | Upgrade kernel-tools-libsUpgrade bpftoolUpgrade kernel-toolsUpgrade kernelUpgrade kernel-abi-stablelistsUpgrade python3-perf | Mar 17, 2026 | Mar 17, 2026 |
| Huawei Euleros 2_0_sp12 | — | Upgrade kernel-toolsUpgrade kernel-tools-libsUpgrade bpftoolUpgrade kernel-abi-stablelistsUpgrade python3-perfUpgrade kernel | Mar 17, 2026 | Mar 17, 2026 |
| Huawei Euleros 2_0_sp13 | — | Upgrade python3-perfUpgrade kernelUpgrade bpftoolUpgrade kernel-tools-libsUpgrade kernel-abi-stablelistsUpgrade kernel-tools | Feb 3, 2026 | Feb 2, 2026 |
| Redhat_linux | — | No solution exists | Jul 17, 2026 | Oct 1, 2025 |
| Ubuntu | — | Upgrade linux-gcp-5.15Upgrade linux-gkeUpgrade linux-azure-5.15Upgrade linux-oracle-5.15Upgrade linux-riscv-5.15Upgrade linux-gkeopUpgrade linux-ibmUpgrade linux-intel-iotg-5.15Upgrade linux-realtimeUpgrade linux-intel-iotgUpgrade linux-nvidiaUpgrade linux-hwe-5.15Upgrade linux-oracleUpgrade linux-gcpUpgrade linux-kvmUpgrade linux-azureUpgrade linux-lowlatencyUpgrade linux-intel-iot-realtimeUpgrade linux-nvidia-tegra-5.15Upgrade linux-awsUpgrade linux-bluefieldUpgrade linux-raspiUpgrade linux-aws-5.15Upgrade linuxUpgrade linux-lowlatency-hwe-5.15 | Oct 10, 2025 | Oct 1, 2025 |
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