Linux: Use After Free
CVE-2026-68121 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 7a56e7c9b08e08fd55a1bcada24cf4fe3782b722, 6eed5ae7887a93160803d2b81ff88e75eefd4a4c, ba3409369c5413cdf0dcbf3a928f76b48e8c3e6a 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 0.37% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 7a56e7c9b08e08fd55a1bcada24cf4fe3782b722 or 6eed5ae7887a93160803d2b81ff88e75eefd4a4c or ba3409369c5413cdf0dcbf3a928f76b48e8c3e6a or e6493a4d1ee17595766165fa446d45b7e0c318d0, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 7a56e7c9b08e08fd55a1bcada24cf4fe3782b722; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 6eed5ae7887a93160803d2b81ff88e75eefd4a4c; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, ba3409369c5413cdf0dcbf3a928f76b48e8c3e6a; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, e6493a4d1ee17595766165fa446d45b7e0c318d0; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 7e9fbd7f96bcde63a7c798fe16b38cedee7a1501; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 6866abf59976d273164a6624234d96a967280223; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, bed4caecd723693f750e13adbb2c42ca1249a3fd; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, e9c238f6fe42fb1b4dba3a578277de32cb487937; and 1 more ranges | 7a56e7c9b08e08fd55a1bcada24cf4fe3782b722, 6eed5ae7887a93160803d2b81ff88e75eefd4a4c, ba3409369c5413cdf0dcbf3a928f76b48e8c3e6a, e6493a4d1ee17595766165fa446d45b7e0c318d0, 7e9fbd7f96bcde63a7c798fe16b38cedee7a1501, 6866abf59976d273164a6624234d96a967280223 |
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
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- 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:L/AC:L/PR:L/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: pppoe: reload header pointer after dev_hard_header() pppoe_sendmsg() saves a pointer to the PPPoE header before calling dev_hard_header(). Device header callbacks are allowed to reallocate the skb head, invalidating pointers into it. This can happen when a send is blocked in copy_from_user() while the first non-Ethernet port is added to an empty team device. The team's delegated GRE header callback then expands the skb head. PPPoE subsequently writes six bytes through the stale pointer into the freed head. Reload the PPPoE header through the skb's network-header offset after device header creation. pskb_expand_head() updates that offset when it relocates the head.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
- git.kernel.org/stable/c/6866abf59976d273164a6624234d96a967280223
- git.kernel.org/stable/c/6eed5ae7887a93160803d2b81ff88e75eefd4a4c
- git.kernel.org/stable/c/7a56e7c9b08e08fd55a1bcada24cf4fe3782b722
- git.kernel.org/stable/c/7e9fbd7f96bcde63a7c798fe16b38cedee7a1501
- git.kernel.org/stable/c/ba3409369c5413cdf0dcbf3a928f76b48e8c3e6a
- git.kernel.org/stable/c/bed4caecd723693f750e13adbb2c42ca1249a3fd
- git.kernel.org/stable/c/e6493a4d1ee17595766165fa446d45b7e0c318d0
- git.kernel.org/stable/c/e9c238f6fe42fb1b4dba3a578277de32cb487937
Recent Use After Free vulnerabilities
- 7.8 High severity
- 9.8 Critical severity
- 7.5 High severity
- 8.8 High severity
- 7.8 High severity
- 7.8 High severity
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