Thumbor treats ALLOWED_SOURCES string patterns as unescaped regex, allowing hostname bypass via wildcard dot
Priority HIGH 75CWE-918Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- High · None · Low
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-1333.
Summary
Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, the ALLOWED_SOURCES configuration passes plain strings to re.match() without escaping dots, so a hostname differing at dot positions can match the allowlist. This issue is fixed in 7.8.0.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00498 42nd 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
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| thumbor | thumbor | before 7.8.0 | 7.8.0 | Patch available | CNA |
| — | thumbor (PyPI) | before 7.8.0 | 7.8.0 | Patch available | GHSA-6x26-6r6f-m537 |
- 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-6x26-6r6f-m537
Remediation
- Fix · CNA thumbor (thumbor) Fixed in 7.8.0
- Fix · GHSA-6x26-6r6f-m537 thumbor (PyPI) Fixed in 7.8.0 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-53500
- 2026-10-03 Alias added: GHSA-6x26-6r6f-m537
References
More thumbor vulnerabilities
- TI-2026-38577 Thumbor has path traversal via post-validation URL decoding bypass in file_loader CVSS 4.0HIGH 8.7
- 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-2026-38578 Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS 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
- CVE-2026-53500 · CVE Program
- CVE-2026-53500 · NVD
- FIRST EPSS
- GHSA-6x26-6r6f-m537 · GitHub Advisory Database · CC BY 4.0
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