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Fencer Intel
high 7.5

CVE-2021-23437 json

Regular Expression Denial of Service (ReDoS)

published 5y ago modified 2mo ago also BIT-pillow-2021-23437 , EUVD-2021-0170 , GHSA-98vv-pw6r-q6q4 , PYSEC-2021-317

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.2%
EPSS 3.2% chance of exploitation in 30 days, percentile 88%
public exploits
0
none known

Summary

The package pillow 5.2.0 and before 8.3.2 are vulnerable to Regular Expression Denial of Service (ReDoS) via the getrgb function.

Patch / fix

  • pypi pillow 8.3.2
  • bitnami pillow 8.3.2
  • n/a Pillow 8.3.2
  • pillow Debian 14, Debian 13, Debian 12 8.3.2-1

debian advisories DEBIAN-CVE-2021-23437

  • pillow Ubuntu 18.04 LTS 5.1.0-1ubuntu0.7
  • pillow Ubuntu 20.04 LTS 7.0.0-4ubuntu0.5
  • pillow Ubuntu 22.04 LTS 9.0.0-1
  • pillow Ubuntu Pro 14.04 LTS 2.3.0-1ubuntu3.4+esm3
  • pillow Ubuntu Pro 16.04 LTS 3.1.2-0ubuntu1.6+esm1

ubuntu advisories UBUNTU-CVE-2021-23437

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-Pillow SLE Module for Package Hub 15 SP6, openSUSE Leap 15.5 7.2.0-150300.3.15.1
  • python-Pillow OpenStack Cloud Crowbar 9, OpenStack Cloud 9 5.2.0-3.14.1
  • python-Pillow OpenStack Cloud Crowbar 8, OpenStack Cloud 8, HPE Helion OpenStack 8 4.2.1-3.20.2

suse advisories SUSE-SU-2024:1673-2SUSE-SU-2024:1673-1SUSE-SU-2021:3235-1SUSE-SU-2021:3234-1

  • python-Pillow openSUSE Tumbleweed 12.3.0-1.1
  • python-Pillow openSUSE Tumbleweed 8.3.2-1.2
  • python-Pillow openSUSE Tumbleweed 10.3.0-1.1

opensuse advisories openSUSE-SU-2026:11261-1openSUSE-SU-2024:11209-1openSUSE-SU-2024:13827-1

  • py-pillow Alpine 3.11 6.2.1-r1
  • py3-pillow Alpine 3.12 7.1.2-r2
  • py3-pillow Alpine 3.13 7.2.0-r2
  • py3-pillow Alpine 3.14 8.2.0-r1
  • py3-pillow Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 8.4.0-r0

alpine advisories ALPINE-CVE-2021-23437

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-pillow Arch Linux 8.3.2-1

arch linux advisories AVG-2366

Is CVE-2021-23437 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2021-23437 updated cvss 7.5

python-pillow: possible ReDoS via the getrgb function

  • Red Hat Quay 3 quay/quay-rhel8
    affected: no fix available
  • Red Hat Enterprise Linux 7 python-pillow, python-pillow-qt, python-pillow-tk, python-pillow-sane Red Hat Enterprise Linux 8 python-pillow, python3-pillow, python3-pillow-tk
    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

3.24% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • snyk.io https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1319443 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
pypi pillow
>=5.2.0, <8.3.2
<8.3.2
8.3.2
bitnami pillow
>=5.2.0, <8.3.2
8.3.2

Affected products

  • n/a Pillow

Classification

Weakness
  • CWE-125 Out-of-bounds Read
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Intel 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.