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TI-2026-38578 Aliases CVE-2026-53503GHSA-cqjp-jf4r-h5q9

Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS

Priority HIGH 72CWE-20Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-369.

Summary

Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(<matrix>, <columns>, <should_normalize>) filter passes the user-controlled <columns> value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns > 0. When columns=0, the C code triggers undefined behavior; on x86_64 this reliably results in a fatal divide-by-zero trap (SIGFPE) and crashes the Thumbor process, causing a remote denial of service. This issue is fixed in 7.8.0.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.0075 55th percentileScored 2026-11-07
Fix Fixed thumbor (thumbor): 7.8.0thumbor (PyPI): 7.8.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
thumborthumborbefore 7.8.07.8.0Patch availableCNA
—thumbor (PyPI)before 7.8.07.8.0Patch availableGHSA-cqjp-jf4r-h5q9
  • thumbor Vendorthumbor Affected before 7.8.0 Fixed in 7.8.0 Patch available CNA
  • thumbor (PyPI) Vendor— Affected before 7.8.0 Fixed in 7.8.0 Patch available GHSA-cqjp-jf4r-h5q9

Remediation

  • Fix · CNA thumbor (thumbor) Fixed in 7.8.0
  • Fix · GHSA-cqjp-jf4r-h5q9 thumbor (PyPI) Fixed in 7.8.0 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-53503
  2. 2026-10-03 Alias added: GHSA-cqjp-jf4r-h5q9

References

Other 4

  • TI-2026-38577 Thumbor has path traversal via post-validation URL decoding bypass in file_loader CVSS 4.0HIGH 8.7
  • TI-2026-38575 Thumbor treats ALLOWED_SOURCES string patterns as unescaped regex, allowing hostname bypass via wildcard dot CVSS 3.1HIGH 8.2
  • TI-2026-38580 Thumbor proportion filter allows unbounded post-transform resize leading to remote DoS CVSS 3.1HIGH 7.5
  • TI-2026-38579 Thumbor has Regex Denial of Service (ReDoS) in `convolution` filter CVSS 3.1HIGH 7.5
  • TI-2026-38576 Thumbor has HMAC validation bypass via multiple .replace() calls when removing URL signature CVSS 3.1HIGH 8.2

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences