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Fencer Vulns
medium 5.5

CVE-2021-20219 json

A denial of service vulnerability was found in n_tty_receive_char_special in drivers/tty/n_tty.c of the Linux kernel.

published 2021-03-23 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-7661

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 34%
public exploits
0
none known

Summary

A denial of service vulnerability was found in n_tty_receive_char_special in drivers/tty/n_tty.c of the Linux kernel. In this flaw a local attacker with a normal user privilege could delay the loop (due to a changing ldata->read_head, and a missing sanity check) and cause a threat to the system availability.

Patch / fix

  • linux linux_kernel 4.18
  • kernel-syms SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +6 more 4.12.14-197.89.2
  • kernel-source SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +6 more 4.12.14-197.89.2
  • kernel-default SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +8 more 4.12.14-197.89.2
  • kernel-zfcpdump SLES 15 SP1-LTSS, Manager Server 4.0 4.12.14-197.89.2
  • kernel-obs-build SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +6 more 4.12.14-197.89.2
  • kernel-syms SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +3 more 4.4.180-94.144.1
  • kernel-source SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +3 more 4.4.180-94.144.1
  • kernel-default SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +4 more 4.4.180-94.144.1

suse advisories SUSE-SU-2021:1624-1SUSE-SU-2021:1623-1SUSE-SU-2021:1617-1SUSE-SU-2021:1596-1SUSE-SU-2021:1573-1SUSE-SU-2021:1266-1

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-2021-20219 updated cvss 6.2

kernel: improper synchronization in flush_to_ldisc() can lead to DoS

  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, kernel-alt, python-perf, +9 more Red Hat Enterprise MRG 2 kernel
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 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

Exploit prediction

0.40% chance of exploitation in the next 30 days, higher than 34% 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
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • n/a kernel

Classification

Weakness
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.