high CVSS 7.5 EPSS 0.36%

CVE-2026-55380·Python vulnerability

Pillow is a Python imaging library. Prior to 12.3.0, PIL/GdImageFile.py GdImageFile._open() read image dimensions from the GD 2.x header and stored them in self._size without calling Image._decompression_bomb_check(), allowing a crafted .gd file to trigger excessive C-heap allocation when loaded. This issue is fixed in version 12.3.0.

Severity
high
Software
Python
Fixed in
12.3.0
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.36% — higher than 28% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-55380 scores 7.5 on CVSS, so a successful attack would be serious — but at 0.36%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

Until: 12.3.0

Fixed in: 12.3.0

How to fix this CVE

Update the Pillow library to version 12.3.0 or later to remediate this decompression bomb vulnerability in GD image file handling. The fix ensures that image dimension validation is properly enforced before memory allocation occurs, preventing maliciously crafted .gd files from causing excessive heap memory consumption. If you use Pillow for image processing, prioritize this update to eliminate the denial-of-service risk.

sudo dnf update python3-pillow

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed Pillow version: python3 -c "import PIL; print(PIL.__version__)"
  2. Verify if your application processes .gd format images: grep -r '\.gd' /path/to/app/config /path/to/app/uploads 2>/dev/null || echo 'No .gd files found in application directories'
  3. Search system logs for memory exhaustion events: grep -i 'out of memory\|oom-killer\|heap' /var/log/syslog /var/log/messages 2>/dev/null | head -20
  4. Confirm the patch: python3 -c "import PIL; print('Patched' if PIL.__version__ >= '12.3.0' else 'Vulnerable')"

FAQ

What is CVE-2026-55380?

CVE-2026-55380 is a denial-of-service vulnerability in Pillow's GD image file parser where crafted .gd files can trigger excessive C-heap memory allocation without proper validation, potentially crashing applications that process untrusted image files.

Is CVE-2026-55380 being actively exploited?

No, CVE-2026-55380 is not listed in CISA's Known Exploited Vulnerabilities catalog and no public exploits are currently available.

What versions of Python are affected by CVE-2026-55380?

The vulnerability affects Pillow versions prior to 12.3.0. Any Python installation using an older version of the Pillow imaging library is at risk.

How do I check if my server is vulnerable to CVE-2026-55380?

Run: python3 -c "import PIL; print(PIL.__version__)" and verify the version is 12.3.0 or later. If it's earlier, your system is vulnerable.

Does Defensia detect CVE-2026-55380?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Pillow is installed on a monitored server, CVE-2026-55380 will appear in your dashboard with remediation steps.

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References

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