How severe is CVE-2026-42309?

CVE-2026-42309 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-42309 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (3rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42309?

CVE-2026-42309 affects Python Pillow. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-42309?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-42309 have an EU (EUVD) identifier?

Yes. CVE-2026-42309 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28901.

When was CVE-2026-42309 published?

CVE-2026-42309 was published on 2026-05-09 and last updated on 2026-06-17.

CVE-2026-42309

CVE-2026-42309 is a medium-severity vulnerability in Python Pillow with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-122.

Key facts

Severity: Medium (CVSS 3.x base score 5.5)
CVSS v4: 5.1
EPSS exploit prediction: 0% (3rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-28901
Weakness: CWE-122
Affected product: Python Pillow
Published: 2026-05-09
Last modified: 2026-06-17

Description

Pillow is a Python imaging library. From version 11.2.1 to before version 12.2.0, passing nested lists as coordinates to APIs that accept coordinates such as ImagePath.Path, ImageDraw.ImageDraw.polygon and ImageDraw.ImageDraw.line could cause a heap buffer overflow, as nested lists were recursively unpacked beyond the allocated buffer. Coordinate lists are now validated to contain exactly two numeric coordinates. This issue has been patched in version 12.2.0.

Frequently asked questions

What is CVE-2026-42309?: Pillow is a Python imaging library. From version 11.2.1 to before version 12.2.0, passing nested lists as coordinates to APIs that accept coordinates such as ImagePath.Path, ImageDraw.ImageDraw.polygon and ImageDraw.ImageDraw.line could cause a heap buffer overflow, as nested lists were recursively unpacked beyond the allocated buffer. Coordinate lists are now validated to contain exactly two numeric coordinates. This issue has been patched in version 12.2.0.
How severe is CVE-2026-42309?: CVE-2026-42309 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-42309 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (3rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42309?: CVE-2026-42309 affects Python Pillow. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-42309?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-42309 have an EU (EUVD) identifier?: Yes. CVE-2026-42309 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28901.
When was CVE-2026-42309 published?: CVE-2026-42309 was published on 2026-05-09 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:python:pillow:*:*:*:*:*:*:*:*

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