CVE-2025-38063: Linux kernel · dm: fix unconditional IO throttle caused by REQ_PREFLUSH
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · fixed in 6.8.0-1046.49~22.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 16:39 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.8.0-1046.49~22.04.1, 6.8.0-1051.57~22.04.1, 6.8.0-1046.53~22.04.1 +33
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 18 Jun 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-aws-6.14pkg:deb/ubuntu/linux-aws-6.14?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
An official patch is available and should be applied to affected Linux kernel versions. The fix conditionally adds the REQ_IDLE flag to flush bios to prevent unnecessary IO throttling. Users should update their Linux kernel to the patched versions as provided by their distribution vendors. No additional mitigation steps are indicated by the vendor advisory.
Description
A vulnerability in the Linux kernel's device mapper (dm) layer caused unconditional IO throttling when a bio with the REQ_PREFLUSH flag was submitted. This led to flush bios being throttled by the writeback throttling mechanism (wbt_wait), indirectly causing metadata IO to be throttled despite prior fixes intended to prevent such throttling. The issue was resolved by conditionally adding the REQ_IDLE flag to flush bios to bypass throttling. This flaw affects specific Linux kernel versions and has a medium severity rating with an available patch.
References
- ubuntu.com/security/CVE-2025-38063 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-38063 (opens in a new tab)
- git.kernel.org/linus/88f7f56d16f568f19e1a695af34a7f4a6ce537a6 (opens in a new tab)
- git.kernel.org/stable/c/2858cda9a8d95e6deee7e3b0a26adde696a9a4f5 (opens in a new tab)
- git.kernel.org/stable/c/52aa28f7b1708d76e315d78b5ed397932a1a97c3 (opens in a new tab)
- git.kernel.org/stable/c/88f7f56d16f568f19e1a695af34a7f4a6ce537a6 (opens in a new tab)
- git.kernel.org/stable/c/95d08924335f3b6f4ea0b92ebfe4fe0731c502d9 (opens in a new tab)
- git.kernel.org/stable/c/b55a97d1bd4083729a60d19beffe85d4c96680de (opens in a new tab)
- ubuntu.com/security/notices/USN-7769-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7770-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7771-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7769-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7769-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7789-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7789-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8031-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-4 (opens in a new tab)