Linux: Use After Free
CVE-2026-63924 is a critical-severity use after 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 b3ac54e5c905f86d22b502eacb5686a282c5659f, 645b99b1a185c91a79bdac4c5de0f91b212d64f0, 9e883eaa878f4337b5873c706efb5a192364ed18 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 0.71% chance of exploitation within 30 days, higher than 54% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to b3ac54e5c905f86d22b502eacb5686a282c5659f or 645b99b1a185c91a79bdac4c5de0f91b212d64f0 or 9e883eaa878f4337b5873c706efb5a192364ed18 or bddaa4dfc7f36e1ee343a0622f69288af2b9ace9, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.259 or 5.15.210 or 6.1.176 or 6.6.143, 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 | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, b3ac54e5c905f86d22b502eacb5686a282c5659f; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 645b99b1a185c91a79bdac4c5de0f91b212d64f0; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 9e883eaa878f4337b5873c706efb5a192364ed18; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, bddaa4dfc7f36e1ee343a0622f69288af2b9ace9; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 72af7beae774e46ed543f3f2f267bf0a141bfcdd; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, c512e1c819dfbf6ae95ee7a44b65b9ad98979157; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 2b56bbd928c030894c270cd33d60286326919458; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, d47548a36639095939f4747d4c43f2271366f565; and 1 more ranges | b3ac54e5c905f86d22b502eacb5686a282c5659f, 645b99b1a185c91a79bdac4c5de0f91b212d64f0, 9e883eaa878f4337b5873c706efb5a192364ed18, bddaa4dfc7f36e1ee343a0622f69288af2b9ace9, 72af7beae774e46ed543f3f2f267bf0a141bfcdd, c512e1c819dfbf6ae95ee7a44b65b9ad98979157 |
| Linux | Linux Kernel | 2.6.12.1 up to, but not including, 5.10.259; 5.11 up to, but not including, 5.15.210; 5.16 up to, but not including, 6.1.176; 6.2 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 2.6.12; and 1 more ranges | 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.35 |
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: ipv6: exthdrs: refresh nh pointer after ipv6_hop_jumbo() ipv6_hop_jumbo() calls pskb_trim_rcsum(), which can change skb pointers. Let's recompute nh pointer to make sure any change won't mess things up.
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: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/2b56bbd928c030894c270cd33d60286326919458
- git.kernel.org/stable/c/645b99b1a185c91a79bdac4c5de0f91b212d64f0
- git.kernel.org/stable/c/72af7beae774e46ed543f3f2f267bf0a141bfcdd
- git.kernel.org/stable/c/9e883eaa878f4337b5873c706efb5a192364ed18
- git.kernel.org/stable/c/b3ac54e5c905f86d22b502eacb5686a282c5659f
- git.kernel.org/stable/c/bddaa4dfc7f36e1ee343a0622f69288af2b9ace9
- git.kernel.org/stable/c/c512e1c819dfbf6ae95ee7a44b65b9ad98979157
- git.kernel.org/stable/c/d47548a36639095939f4747d4c43f2271366f565
Recent Use After Free vulnerabilities
- 8.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 9.8 Critical severity
- 8.8 High severity
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