synced 14 MIN AGO
01 Record

CVE-2021-20177

A flaw was found in the Linux kernel's implementation of string matching within a packet. A privileged user (with root or CAP_NET_ADMIN) when inserting iptables rules could insert a rule which can

UnratedPUBLISHEDCNA: redhat
CNA base scoreUnratedNo CNA CVSS vector

02 Description

A flaw was found in the Linux kernel's implementation of string matching within a packet. A privileged user (with root or CAP_NET_ADMIN) when inserting iptables rules could insert a rule which can

03 Exploitation and scoring

Exploitation
Not assessed. CISA has not published an exploitation assessment for this record, and it is not in the KEV catalog. That is an absence of assessment, not a finding of no risk.
SSVC decision
Not assessed by CISA
EPSS probability
0.28% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 20.6% of scored records. A rank, not a probability.
NVD base score
4.4 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
NVD analysis status
Modified. NVD last modified this record on 2026-06-17.
Red Hat severity
Moderate. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2021-05-26 20:48Z5 YR AGO
Last updated
2024-08-03 17:30Z2 YR AGO
Reserved
2020-12-17
Assigning CNA
redhat
Record state
PUBLISHED
Severity
Not rated by the issuing CNA
CNA CVSS vector
Not published by the issuing CNA
Weaknesses
Data version
5.1
Document digest
61aad8b8d101241eef0bacca16978fc65e7882dd975e4855e553cd57326eca40

05 Affected products

VendorProductVersionsPlatforms
n/akernelkernel 5.5-rc1—

06 References

07 Fixed in

Arch Linux

  • linux-lts
    Fixed in 5.4.81-1

Source: Arch Linux Security Tracker, the Arch Linux security team. Reformatted by exploit.cc.

Debian 12

  • linux
    Fixed in 5.5.13-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

  • linux
    Fixed in 5.5.13-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

  • linux
    Fixed in 5.5.13-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 16.04 LTS

  • linux-hwe-edge
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 18.04 LTS

  • linux-aws-5.0
    No fix yet
  • linux-aws-5.3
    No fix yet
  • linux-aws-5.4
    Fixed in 5.4.0-1038.40~18.04.1
  • linux-azure
    No fix yet
  • linux-azure-5.3
    No fix yet
  • linux-azure-5.4
    Fixed in 5.4.0-1040.42~18.04.1
  • linux-azure-edge
    No fix yet
  • linux-gcp
    No fix yet
  • linux-gcp-5.3
    No fix yet
  • linux-gcp-5.4
    Fixed in 5.4.0-1037.40~18.04.1
  • linux-gcp-edge
    No fix yet
  • linux-gke-5.4
    Fixed in 5.4.0-1036.38~18.04.1
  • linux-gkeop-5.4
    Fixed in 5.4.0-1010.11~18.04.1
  • linux-hwe
    No fix yet
  • linux-hwe-5.4
    Fixed in 5.4.0-66.74~18.04.2
  • linux-hwe-edge
    No fix yet
  • linux-oem
    No fix yet
  • linux-oracle-5.0
    No fix yet
  • linux-oracle-5.3
    No fix yet
  • linux-oracle-5.4
    Fixed in 5.4.0-1038.41~18.04.1
  • linux-raspi-5.4
    Fixed in 5.4.0-1029.32~18.04.1

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 20.04 LTS

  • linux
    Fixed in 5.4.0-66.74
  • linux-aws
    Fixed in 5.4.0-1038.40
  • linux-azure
    Fixed in 5.4.0-1040.42
  • linux-gcp
    Fixed in 5.4.0-1037.40
  • linux-gke
    Fixed in 5.4.0-1036.38
  • linux-gkeop
    Fixed in 5.4.0-1010.11
  • linux-kvm
    Fixed in 5.4.0-1033.34
  • linux-oracle
    Fixed in 5.4.0-1038.41
  • linux-raspi
    Fixed in 5.4.0-1029.32
  • linux-raspi2
    No fix yet
  • linux-riscv
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 22.04 LTS

  • linux-intel-iot-realtime
    No fix yet
  • linux-realtime
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 24.04 LTS

  • linux-raspi-realtime
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro FIPS-updates 20.04 LTS

  • linux-aws-fips
    Fixed in 5.4.0-1069.73+fips2
    Available with Ubuntu Pro: https://ubuntu.com/pro
  • linux-azure-fips
    Fixed in 5.4.0-1073.76+fips1
    Available with Ubuntu Pro: https://ubuntu.com/pro
  • linux-gcp-fips
    Fixed in 5.4.0-1067.71~20.04.1
    Available with Ubuntu Pro: https://ubuntu.com/pro

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro FIPS 20.04 LTS

  • linux-aws-fips
    No fix yet
  • linux-azure-fips
    No fix yet
  • linux-gcp-fips
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.