CVE-2026-23352: Linux kernel · x86/efi: defer freeing of boot services memory
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 5.5 Medium · fixed in 5.15.0-1112.119~20.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 16:03 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 5.15.0-1112.119~20.04.1, 5.15.0-1117.126~20.04.1, 5.15.0-1117.126~20.04.2 +63
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 25 Mar 2026
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 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=questingOther 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
A patch is available that addresses this issue by deferring the freeing of EFI boot services memory until after deferred memory map initialization completes. Users should apply the official Linux kernel updates that include this fix. The vendor advisory confirms that this vulnerability has been resolved in updated kernel versions.
Description
A vulnerability in the Linux kernel's x86 EFI boot services memory freeing process was resolved. The issue involves improper handling of EFI boot services memory freeing, causing a memory leak of approximately 140MB on certain EC2 instances with limited RAM. The problem arises because the memory freeing function is called before the memory map initialization completes, leading to skipped freeing of uninitialized pages. The fix splits the freeing process into two phases to defer actual freeing until after initialization is complete, avoiding concurrency issues late in boot.
References
- ubuntu.com/security/CVE-2026-23352 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-23352 (opens in a new tab)
- git.kernel.org/linus/a4b0bf6a40f3c107c67a24fbc614510ef5719980 (opens in a new tab)
- git.kernel.org/stable/c/227688312fece0026fc67a00ba9a0b3611ebe95d (opens in a new tab)
- git.kernel.org/stable/c/399da820ecfe6f4f10c143e5c453d3559a04db9c (opens in a new tab)
- git.kernel.org/stable/c/4a2cb90c538f06c873a187aa743575d48685d7a6 (opens in a new tab)
- git.kernel.org/stable/c/6a25e25279282c5c8ade554c04c6ab9dc7902c64 (opens in a new tab)
- git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326 (opens in a new tab)
- git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980 (opens in a new tab)
- git.kernel.org/stable/c/f9e9cc320854a76a39e7bc92d144554f3a727fad (opens in a new tab)
- ubuntu.com/security/notices/USN-8567-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8575-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8576-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8574-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8595-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8596-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8575-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8576-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8597-1 (opens in a new tab)