CVE-2026-43050 [High] | Use-After-Free in Linux Kernel

In the Linux kernel, the following vulnerability has been resolved: atm: lec: fix use-after-free in sock_def_readable() A race condition exists between lec_atm_close() setting priv->lecd to NULL and concurrent access to priv->lecd in send_to_lecd(), lec_handle_bridge(), and lec_atm_send(). When the socket is freed via RCU while another thread is still using it, a use-after-free occurs in sock_def_readable() when accessing the socket's wait queue. The root cause is that lec_atm_close() clears priv->lecd without any synchronization, while callers dereference priv->lecd without any protection against concurrent teardown. Fix this by converting priv->lecd to an RCU-protected pointer: - Mark priv->lecd as __rcu in lec.h - Use rcu_assign_pointer() in lec_atm_close() and lecd_attach() for safe pointer assignment - Use rcu_access_pointer() for NULL checks that do not dereference the pointer in lec_start_xmit(), lec_push(), send_to_lecd() and lecd_attach() - Use rcu_read_lock/rcu_dereference/rcu_read_unlock in send_to_lecd(), lec_handle_bridge() and lec_atm_send() to safely access lecd - Use rcu_assign_pointer() followed by synchronize_rcu() in lec_atm_close() to ensure all readers have completed before proceeding. This is safe since lec_atm_close() is called from vcc_release() which holds lock_sock(), a sleeping lock. - Remove the manual sk_receive_queue drain from lec_atm_close() since vcc_destroy_socket() already drains it after lec_atm_close() returns. v2: Switch from spinlock + sock_hold/put approach to RCU to properly fix the race. The v1 spinlock approach had two issues pointed out by Eric Dumazet: 1. priv->lecd was still accessed directly after releasing the lock instead of using a local copy. 2. The spinlock did not prevent packets being queued after lec_atm_close() drains sk_receive_queue since timer and workqueue paths bypass netif_stop_queue(). Note: Syzbot patch testing was attempted but the test VM terminated unexpectedly with "Connection to localhost closed by remote host", likely due to a QEMU AHCI emulation issue unrelated to this fix. Compile testing with "make W=1 net/atm/lec.o" passes cleanly.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-02	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-02

—

0.02%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.0	3.1	HIGH	`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:H) Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.0	5.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.0

3.1

HIGH

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H): Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.0

5.9

[email protected]

OS Trackers for CVE-2026-43050

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2026-43050 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6.	https://security-tracker.debian.org/tracker/CVE-2026-43050
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2026-43050
`suse`	high	—	https://www.suse.com/security/cve/CVE-2026-43050/
`ubuntu`	medium	CVE-2026-43050 medium priority: Ubuntu including 161 source packages (linux, linux-allwinner-5.19, …), 1449 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): DNE 1048, ignored 173, needed 130, released 83, not-affected 10, needs-triage 5.	https://ubuntu.com/security/CVE-2026-43050

Affected software / configurations for CVE-2026-43050

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 2.6.12.1, < 5.10.253	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.11, < 5.15.203	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.16, < 6.1.168	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.2, < 6.6.134	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.7, < 6.12.81	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.18.22	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.19, < 6.19.12	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	2.6.12	cpe:2.3:o:linux:linux_kernel:2.6.12:-::::::
linux	linux_kernel	2.6.12	cpe:2.3:o:linux:linux_kernel:2.6.12:rc2::::::
linux	linux_kernel	2.6.12	cpe:2.3:o:linux:linux_kernel:2.6.12:rc3::::::
linux	linux_kernel	2.6.12	cpe:2.3:o:linux:linux_kernel:2.6.12:rc4::::::
linux	linux_kernel	2.6.12	cpe:2.3:o:linux:linux_kernel:2.6.12:rc5::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc1::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc2::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc3::::::
linux	linux_kernel	7.0	cpe:2.3:o:linux:linux_kernel:7.0:rc4::::::

References for CVE-2026-43050

URL	Tags
https://git.kernel.org/stable/c/317843d5355062020649124eb4a0d7acbcc3f53e	Patch
https://git.kernel.org/stable/c/3989740fa4978e1d2d51ecc62be1b01093e104ad	Patch
https://git.kernel.org/stable/c/3e8b25f32f2f35549d03d77da030a24a45bdef5b	Patch
https://git.kernel.org/stable/c/5fbbb1ff936d7ff9528d929c1549977e8123d8a8	Patch
https://git.kernel.org/stable/c/750a33f417f3d196b86375f8d9f8938bacf130fe	Patch
https://git.kernel.org/stable/c/922814879542c2e397b0e9641fd36b8202a8e555	Patch
https://git.kernel.org/stable/c/abc10f85a3965ac14b9ed7ad3e67b35604a63aa3	Patch
https://git.kernel.org/stable/c/b256d055da47258e63f8b40965f276c5f23d229a	Patch

URL

CVE-2026-43050 | atm: lec: fix use-after-free in sock_def_readable()

Exploit prediction scoring system (EPSS) score for CVE-2026-43050

Common vulnerability scoring system (CVSS) metrics for CVE-2026-43050

Weakness enumeration for CVE-2026-43050

GitHub Security Advisory for CVE-2026-43050

OS Trackers for CVE-2026-43050

Affected software / configurations for CVE-2026-43050

References for CVE-2026-43050