Bug 2468257 (CVE-2026-43458)

Summary: CVE-2026-43458 kernel: serial: caif: hold tty->link reference in ldisc_open and ser_release
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel, specifically within the `caif_serial` line discipline. This vulnerability, a use-after-free, occurs due to improper management of the `tty->link` reference during the `ldisc_open` and `ser_release` functions. A local attacker could exploit this by triggering the `caif_serial` transmit path, which may lead to a system crash, resulting in a Denial of Service (DoS), or potentially allow for privilege escalation.
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Description OSIDB Bzimport 2026-05-08 15:07:23 UTC 
In the Linux kernel, the following vulnerability has been resolved:

serial: caif: hold tty->link reference in ldisc_open and ser_release

A reproducer triggers a KASAN slab-use-after-free in pty_write_room()
when caif_serial's TX path calls tty_write_room(). The faulting access
is on tty->link->port.

Hold an extra kref on tty->link for the lifetime of the caif_serial line
discipline: get it in ldisc_open() and drop it in ser_release(), and
also drop it on the ldisc_open() error path.

With this change applied, the reproducer no longer triggers the UAF in
my testing.
Comment 1 Keith Grant 2026-05-09 00:58:23 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026050800-CVE-2026-43458-d72f@gregkh/T