Linux: Double Free
CVE-2026-31608 is a critical-severity double free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 6968c91fab05b8fc4d6700e0cf34472bb422df25, 2ba03f46132b0d1a7bafb86e1ef61951a2254023, 830de6eeb9db4cb7e758201fb99328ef4ca4b032 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.46% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 6968c91fab05b8fc4d6700e0cf34472bb422df25 or 2ba03f46132b0d1a7bafb86e1ef61951a2254023 or 830de6eeb9db4cb7e758201fb99328ef4ca4b032 or 84ff995ae826aa6bbcc6c7b9ea569ff67c021d72, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.18.24 or 6.19.14 or 7.0.1, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 5ef18a2e66f2f33fdac64437bddfb9fe6389fdc7 up to, but not including, 6968c91fab05b8fc4d6700e0cf34472bb422df25; 79242e7b6bc63efec28b7c235bc320806afce6c0 up to, but not including, 2ba03f46132b0d1a7bafb86e1ef61951a2254023; 34abd408c8ba24d7c97bd02ba874d8c714f49db1 up to, but not including, 830de6eeb9db4cb7e758201fb99328ef4ca4b032; 34abd408c8ba24d7c97bd02ba874d8c714f49db1 up to, but not including, 84ff995ae826aa6bbcc6c7b9ea569ff67c021d72; 6.18.11 up to, but not including, 6.18.24; 6.19.1 up to, but not including, 6.19.14; 7.0 | 6968c91fab05b8fc4d6700e0cf34472bb422df25, 2ba03f46132b0d1a7bafb86e1ef61951a2254023, 830de6eeb9db4cb7e758201fb99328ef4ca4b032, 84ff995ae826aa6bbcc6c7b9ea569ff67c021d72, 6.18.24, 6.19.14 |
| Linux | Linux Kernel | before 6.18.24; 6.19 up to, but not including, 6.19.14; 7.0 up to, but not including, 7.0.1 | 6.18.24, 6.19.14, 7.0.1 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: smb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list() smb_direct_flush_send_list() already calls smb_direct_free_sendmsg(), so we should not call it again after post_sendmsg() moved it to the batch list.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Double Free
The product calls free() twice on the same memory address.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.
- Use a static analysis tool to find double free instances.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Double Free vulnerabilities
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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