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Fencer Vulns
medium 5.5

CVE-2026-23472 json

serial: core: fix infinite loop in handle_tx() for PORT_UNKNOWN

published 2026-04-03 7 mo ago modified 2026-11-05 3 d ago also EUVD-2026-18745

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 5%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

serial: core: fix infinite loop in handle_tx() for PORT_UNKNOWN

uart_write_room() and uart_write() behave inconsistently when xmit_buf is NULL (which happens for PORT_UNKNOWN ports that were never properly initialized):

- uart_write_room() returns kfifo_avail() which can be > 0 - uart_write() checks xmit_buf and returns 0 if NULL

This inconsistency causes an infinite loop in drivers that rely on tty_write_room() to determine if they can write:

while (tty_write_room(tty) > 0) { written = tty->ops->write(...); // written is always 0, loop never exits }

For example, caif_serial's handle_tx() enters an infinite loop when used with PORT_UNKNOWN serial ports, causing system hangs.

Fix by making uart_write_room() also check xmit_buf and return 0 if it's NULL, consistent with uart_write().

Reproducer: https://gist.github.com/mrpre/d9a694cc0e19828ee3bc3b37983fde13

Patch / fix

  • Linux Linux 6.1.191, 6.6.160, 6.12.114, 6.18.20, 6.19.10, 7.0
  • linux Debian 13 6.12.115-2
  • linux Debian 14 6.19.10-1

debian advisories DEBIAN-CVE-2026-23472

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.55.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.55.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.55.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.55.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.55.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.55.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.55.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.55.1.150700.17.33.1

suse advisories SUSE-SU-2026:2238-1SUSE-SU-2026:21834-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-23472 updated cvss 5.5

kernel: serial: core: fix infinite loop in handle_tx() for PORT_UNKNOWN

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 d ago

Exploit prediction

0.16% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.