CVE-2026-54059Public exploitNetwork attack vector

Memory exhaustion via unchecked PCF glyph dimensions

Published Jul 6, 2026 · Updated Jul 6, 2026

Unchecked PCF font dimensions in Pillow before 12.3.0 allow attackers to exhaust memory by loading a crafted PCF font. PcfFontFile._load_bitmaps() passes attacker-controlled METRICS widths and heights to Image.frombytes() without the decompression-bomb check, allocating up to about 1.07 GB per glyph. Exploitation requires an application to pass an untrusted PCF stream directly to PcfFontFile; Image.open() does not invoke this loader, and memory exhaustion can interrupt the hosting service.

CVSS severity7.5
High
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unchecked PCF font dimensions in Pillow before 12.3.0 allow attackers to exhaust memory by loading a crafted PCF font. PcfFontFile._load_bitmaps() passes attacker-controlled METRICS widths and heights to Image.frombytes() without the decompression-bomb check, allocating up to about 1.07 GB per glyph. Exploitation requires an application to pass an untrusted PCF stream directly to PcfFontFile; Image.open() does not invoke this loader, and memory exhaustion can interrupt the hosting service.

The record

CVE
CVE-2026-54059
Published
Jul 6, 2026
Updated
Jul 6, 2026
Vendor
Pillow
Product
Pillow
Classifications
CWE-789, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 6, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 12.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Pillow · Pillowversion=< 12.3.0

Published CVSS scores

7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-789Memory Allocation with Excessive Size Value
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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