Linux: Use After Free
CVE-2026-64557 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. The record lists versions b39298044e5534612511a2ff5de03ba5f6e7a820, 8c37e4338c801ebb8cee52436c01c41e009f6e87, 84e718b6a814edc84159361f9f454a4e92ae91ae 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 0.29% 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 b39298044e5534612511a2ff5de03ba5f6e7a820 or 8c37e4338c801ebb8cee52436c01c41e009f6e87 or 84e718b6a814edc84159361f9f454a4e92ae91ae or 36da806f7fbaee56ad9e81859deec203f9728700, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.178 or 6.6.145 or 6.12.97 or 6.18.40, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 8ffb929098a56939ac71509302eeab5b207bf262 up to, but not including, b39298044e5534612511a2ff5de03ba5f6e7a820; 8ffb929098a56939ac71509302eeab5b207bf262 up to, but not including, 8c37e4338c801ebb8cee52436c01c41e009f6e87; 8ffb929098a56939ac71509302eeab5b207bf262 up to, but not including, 84e718b6a814edc84159361f9f454a4e92ae91ae; 8ffb929098a56939ac71509302eeab5b207bf262 up to, but not including, 36da806f7fbaee56ad9e81859deec203f9728700; 8ffb929098a56939ac71509302eeab5b207bf262 up to, but not including, 733e76e74e406c1d1ddc7369420dd8a47f48bb8a; 8ffb929098a56939ac71509302eeab5b207bf262 up to, but not including, 6fef032af0092ed5ccb767239a9ac1bc38c08a40; 3.13 | b39298044e5534612511a2ff5de03ba5f6e7a820, 8c37e4338c801ebb8cee52436c01c41e009f6e87, 84e718b6a814edc84159361f9f454a4e92ae91ae, 36da806f7fbaee56ad9e81859deec203f9728700, 733e76e74e406c1d1ddc7369420dd8a47f48bb8a, 6fef032af0092ed5ccb767239a9ac1bc38c08a40 |
| Linux | Linux Kernel | 3.13 up to, but not including, 6.1.178; 6.2 up to, but not including, 6.6.145; 6.7 up to, but not including, 6.12.97; 6.13 up to, but not including, 6.18.40; 6.19 up to, but not including, 7.1.5; 7.2 | 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5 |
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
- AdjacentThe attacker must be on the same local network segment.
- 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:A/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: Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_new_connection_cb() l2cap_sock_new_connection_cb() returned l2cap_pi(sk)->chan after release_sock(parent). Once the parent lock is dropped the newly enqueued child socket sk is reachable via the accept queue, so another task can accept and free it before the callback dereferences sk, resulting in a use-after-free. Rework the ->new_connection() op so the core, rather than the callback, owns the child channel's lifetime. The op now receives a pre-allocated new_chan and returns an errno instead of allocating and returning a channel. l2cap_new_connection() allocates the child channel and links it into the conn list via __l2cap_chan_add() before invoking the callback, so the conn-list reference keeps the channel alive once release_sock(parent) exposes the socket to other tasks. Channel configuration that was duplicated in l2cap_sock_init() and the various new_connection callbacks is consolidated into l2cap_chan_set_defaults(), which now inherits from the parent channel when one is supplied.
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
Patches and release notes
- git.kernel.org/stable/c/36da806f7fbaee56ad9e81859deec203f9728700
- git.kernel.org/stable/c/6fef032af0092ed5ccb767239a9ac1bc38c08a40
- git.kernel.org/stable/c/733e76e74e406c1d1ddc7369420dd8a47f48bb8a
- git.kernel.org/stable/c/84e718b6a814edc84159361f9f454a4e92ae91ae
- git.kernel.org/stable/c/8c37e4338c801ebb8cee52436c01c41e009f6e87
- git.kernel.org/stable/c/b39298044e5534612511a2ff5de03ba5f6e7a820
Recent Use After Free vulnerabilities
- 7.8 High severity
- 9.8 Critical severity
- 7.5 High severity
- 8.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
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