high CVSS 7.5

CVE-2026-40192·Python vulnerability

Pillow is a Python imaging library. Versions 10.3.0 through 12.1.1 did not limit the amount of GZIP-compressed data read when decoding a FITS image, making them vulnerable to decompression bomb attacks. A specially crafted FITS file could cause unbounded memory consumption, leading to denial of service (OOM crash or severe performance degradation). If users are unable to immediately upgrade, they should only open specific image formats, excluding FITS, as a workaround.

Severity
high
Software
Python
Fixed in
12.2.0
Published
2026-04-15

Affected versions

From: 10.3.0

Until: 12.2.0

Fixed in: 12.2.0

How to fix this CVE

Update Pillow to version 12.2.0 or later to address a decompression bomb vulnerability in FITS image handling that can exhaust system memory. This fix implements proper limits on GZIP-compressed data during FITS decoding, preventing resource exhaustion attacks. Organizations running Python applications that process image files should 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. Run `python3 -c "from PIL import Image; print(Image.__version__)"` to check the installed Pillow version
  2. Query package manager: `dpkg -l | grep python3-pil` (Debian/Ubuntu) or `rpm -q python3-pillow` (RHEL/CentOS/Amazon Linux)
  3. Monitor system logs for OOM killer events or sudden memory spikes: `grep -i 'oom-kill\|out of memory' /var/log/syslog /var/log/messages`
  4. Verify the patch by confirming Pillow version is 12.2.0 or higher and attempting to decode a test FITS file to ensure decompression limits are enforced

FAQ

What is CVE-2026-40192?

CVE-2026-40192 is a vulnerability in Pillow's FITS image decoder that fails to impose limits on GZIP decompression, allowing attackers to craft malicious FITS files that consume excessive memory and crash applications or servers.

Is CVE-2026-40192 being actively exploited?

No, this vulnerability is not currently listed on the CISA Known Exploited Vulnerabilities catalog and no public exploits are available, though the risk remains significant for systems processing untrusted image files.

What versions of Python are affected by CVE-2026-40192?

Pillow versions 10.3.0 through 12.1.1 are affected; version 12.2.0 and later contain the fix.

How do I check if my server is vulnerable to CVE-2026-40192?

Run `python3 -c "from PIL import Image; print(Image.__version__)"` and compare against version 12.2.0; if installed version is 10.3.0–12.1.1, your system is vulnerable.

Does Defensia detect CVE-2026-40192?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Pillow/Python is installed on a monitored server, CVE-2026-40192 will appear in your dashboard with remediation steps.

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References

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