Linux: Use After Free
CVE-2026-63922 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, f8aabed3ff3e986920cf02a2a2785e08e586b234, 1a11eb7431e3d2882f5bd5939c5a9bbc65ccf4d1 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 f8aabed3ff3e986920cf02a2a2785e08e586b234 or 1a11eb7431e3d2882f5bd5939c5a9bbc65ccf4d1 or 12d957979e4a800167842f1b42be6a606d227ebe, 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 | a831f5bbc89a9978795504be9e1ff412043f8f77 up to, but not including, b3ac54e5c905f86d22b502eacb5686a282c5659f; a831f5bbc89a9978795504be9e1ff412043f8f77 up to, but not including, f8aabed3ff3e986920cf02a2a2785e08e586b234; a831f5bbc89a9978795504be9e1ff412043f8f77 up to, but not including, 1a11eb7431e3d2882f5bd5939c5a9bbc65ccf4d1; a831f5bbc89a9978795504be9e1ff412043f8f77 up to, but not including, 12d957979e4a800167842f1b42be6a606d227ebe; a831f5bbc89a9978795504be9e1ff412043f8f77 up to, but not including, ff375ed1cba81392346c5bfbf0bb7a13b2946f99; a831f5bbc89a9978795504be9e1ff412043f8f77 up to, but not including, 751db1b802a067b7fff25880f4e9f9152a171538; a831f5bbc89a9978795504be9e1ff412043f8f77 up to, but not including, 9b6dcc0a39fd71752937f0b6b3973e1416085dcf; a831f5bbc89a9978795504be9e1ff412043f8f77 up to, but not including, f7b52afe3592eae66e160586b45a3f2242972c63; and 1 more ranges | b3ac54e5c905f86d22b502eacb5686a282c5659f, f8aabed3ff3e986920cf02a2a2785e08e586b234, 1a11eb7431e3d2882f5bd5939c5a9bbc65ccf4d1, 12d957979e4a800167842f1b42be6a606d227ebe, ff375ed1cba81392346c5bfbf0bb7a13b2946f99, 751db1b802a067b7fff25880f4e9f9152a171538 |
| Linux | Linux Kernel | 2.6.19 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; 7.1 | 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 after handling HAO option ip6_parse_tlv() caches skb_network_header(skb) in nh while walking IPv6 TLVs. ipv6_dest_hao() may call pskb_expand_head() for a cloned skb, which can move the skb head and invalidate the cached network header pointer. Refresh nh after ipv6_dest_hao() returns so any trailing padding or TLVs are parsed from the current skb head. This matches the existing pattern used in ip6_parse_tlv() after helpers that can modify skb header storage.
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/12d957979e4a800167842f1b42be6a606d227ebe
- git.kernel.org/stable/c/1a11eb7431e3d2882f5bd5939c5a9bbc65ccf4d1
- git.kernel.org/stable/c/751db1b802a067b7fff25880f4e9f9152a171538
- git.kernel.org/stable/c/9b6dcc0a39fd71752937f0b6b3973e1416085dcf
- git.kernel.org/stable/c/b3ac54e5c905f86d22b502eacb5686a282c5659f
- git.kernel.org/stable/c/f7b52afe3592eae66e160586b45a3f2242972c63
- git.kernel.org/stable/c/f8aabed3ff3e986920cf02a2a2785e08e586b234
- git.kernel.org/stable/c/ff375ed1cba81392346c5bfbf0bb7a13b2946f99
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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