High [CVE-2026-68143] Linux kernel SLIP: Out-of-bounds write due to race condition during MTU change
This high-severity Red Hat Linux advisory covers CVE-2026-68143 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
In the Linux kernel, the following vulnerability has been resolved: net: slip: serialize receive against buffer reallocation sl_realloc_bufs() replaces rbuff and updates buffsize while holding sl->lock. slip_receive_buf() reads those fields and writes through rbuff without holding the lock. An MTU change can therefore race with receive processing.
An MTU shrink can expose the new smaller rbuff with the old larger bound, causing an out-of-bounds write. A receive callback which already loaded the old rbuff can instead continue writing after that buffer has been freed.
A flaw was found in the Linux kernel's SLIP (Serial Line Internet Protocol) network component. A race condition exists during an MTU (Maximum Transmission Unit) change when the system reallocates receive buffers.
This can allow a remote attacker to trigger an out-of-bounds write or write to a freed memory region, potentially leading to a denial of service or arbitrary code execution. Red Hat severity: Important — CVSS 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
Weakness: CWE-787. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9.
Red Hat does not currently list a fixing RHSA for this CVE.
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 30 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 30 days ago·verify at source
Mitigation checklist
- To mitigate this vulnerability, prevent the `slip` kernel module from loading if the SLIP protocol is not required. Create a file `/etc/modprobe.d/disable-slip.conf` with the content `blacklist slip`. Then, regenerate the initramfs using `dracut -f -v`. A system reboot is required for the changes to be fully applied. This action may impact systems relying on the SLIP protocol for network communication.
Official advisory · high-confidence parse· fetched 30 days ago·verify at source
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