High [CVE-2026-72243] check connect-related permissions on TCP Fast Open
This high-severity Red Hat Linux advisory covers CVE-2026-72243 affecting Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6.
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Summary
In the Linux kernel, the following vulnerability has been resolved: selinux: check connect-related permissions on TCP Fast Open Similar to Landlock, SELinux was not updated when TCP Fast Open support was introduced to ensure connect-related permissions are checked when using TCP Fast Open.
Update its socket_sendmsg() hook to call selinux_socket_connect() when MSG_FASTOPEN is passed. This oversight could allow a local attacker to bypass SELinux network access controls, potentially enabling unauthorized network connections that should have been restricted by security policies.
Red Hat severity: Important — CVSS 7.3 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L). Weakness: CWE-551.
Affected Red Hat products: Red Hat Enterprise Linux 9; Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8. Will not fix / out of support: Red Hat Enterprise Linux 8.
Red Hat fixing advisory: RHSA-2026:68570.
Affected products named by the advisory: Red Hat package: kernel-rt.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 22 days ago·verify at source
- kernel-0:5.14.0-687.49.1.el9_8
- RHSA-2026:68570
Official advisory · high-confidence parse· fetched 22 days ago·verify at source
Mitigation checklist
- To mitigate this issue, TCP Fast Open (TFO) can be disabled if not required by applications. Disabling TFO prevents the vulnerable code path from being exercised, thereby eliminating the SELinux permission bypass. To disable TCP Fast Open: 1. Check the current setting: `sysctl net.ipv4.tcp_fastopen` 2. To disable it temporarily: `sudo sysctl -w net.ipv4.tcp_fastopen=0` 3. To make the change persistent across reboots, add or modify the following line in `/etc/sysctl.conf`: `net.ipv4.tcp_fastopen = 0` 4. Apply the persistent changes: `sudo sysctl -p` Disabling TCP Fast Open may impact the performance of applications that utilize this feature for faster connection establishment.
Official advisory · high-confidence parse· fetched 22 days ago·verify at source
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