CVE-2021-23437

HIGHNVD 7.57.5—

7.5

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

CVSS v3: 7.5
EG Score: 7.5(medium)
EPSS: 45.3%
KEV: Not listed

Published

September 3, 2021

Last Modified

November 21, 2024

References (14)

report@snykhttps://github.com/python-pillow/Pillow/commit/9e08eb8f78fdfd2f476e1b20b7cf38683754866b
report@snykhttps://lists.debian.org/debian-lts-announce/2024/03/msg00021.html
report@snykhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RNSG6VFXTAROGF7ACYLMAZNQV4EJ6I2C/
report@snykhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VKRCL7KKAKOXCVD7M6WC5OKFGL4L3SJT/
report@snykhttps://pillow.readthedocs.io/en/stable/releasenotes/8.3.2.html
report@snykhttps://security.gentoo.org/glsa/202211-10
report@snykhttps://snyk.io/vuln/SNYK-PYTHON-PILLOW-1319443
af854a3a-2127-422b-91ae-364da2661108https://github.com/python-pillow/Pillow/commit/9e08eb8f78fdfd2f476e1b20b7cf38683754866b
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2024/03/msg00021.html
af854a3a-2127-422b-91ae-364da2661108https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RNSG6VFXTAROGF7ACYLMAZNQV4EJ6I2C/
af854a3a-2127-422b-91ae-364da2661108https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VKRCL7KKAKOXCVD7M6WC5OKFGL4L3SJT/
af854a3a-2127-422b-91ae-364da2661108https://pillow.readthedocs.io/en/stable/releasenotes/8.3.2.html
af854a3a-2127-422b-91ae-364da2661108https://security.gentoo.org/glsa/202211-10
af854a3a-2127-422b-91ae-364da2661108https://snyk.io/vuln/SNYK-PYTHON-PILLOW-1319443

Patch Availability(2)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
ubuntu	python3-pil (8.1.2+dfsg-0.3ubuntu0.1) @ impish	2026-05-26	ubuntu
ubuntu	python3-pil.imagetk (3.1.2-0ubuntu1.6+esm1) @ xenial	2026-05-26	ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)

PyPI(1)

Package	Vulnerable range	Fixed in	Dependents
pillow	1.0 ... 8.3.1 (82 versions)	8.3.2	—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-125Out-of-bounds Read

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 8× in last 7d / 8× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-27 13:39 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 11:04 UTCEG score recompute
2026-05-26 11:04 UTCVendor advisory
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-24 16:49 UTCepss_batch

Frequently asked(5)

What is CVE-2021-23437?

CVE-2021-23437 is a high vulnerability published on September 3, 2021. The package pillow 5.2.0 and before 8.3.2 are vulnerable to Regular Expression Denial of Service (ReDoS) via the getrgb function.

When was CVE-2021-23437 disclosed?

CVE-2021-23437 was first published in the National Vulnerability Database on September 3, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-23437 actively exploited?

CVE-2021-23437 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 45.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-23437?

CVE-2021-23437 has a CVSS v3 base score of 7.5 (NVD).

How do I remediate CVE-2021-23437?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-23437, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-23437

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CVE-2021-23437

Published

Last Modified

References (14)

Patch Availability(2)

Affected Packages

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-23437?

Same vendor

Same CWE

CVE-2021-23437

📅 Published

🔄 Last Modified

🔗 References (14)

Patch Availability(2)

Affected Packages

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-23437?

🔗 Related CVEs(same vendor + same CWE)

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Last Modified

References (14)

Frequently asked(5)

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