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CVE-2026-53502— Thumbor has path traversal via post-validation URL decoding bypass in file_loader

Quick assessment

Affected
thumbor thumbor
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

thumbor thumbor是thumbor组织开源的一个图像处理服务。 thumbor 7.8.0之前版本存在路径遍历漏洞，该漏洞源于file_loader在根边界验证后解码百分号编码的路径段，可通过watermark或frame filter输入进行路径遍历，导致访问FILE_LOADER_ROOT_PATH之外的文件。

CVSS 8.7 · High EPSS 0.36% · P29

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 1

VendorProduct Version RangeStatus
thumbor thumbor < 7.8.0 affected
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I. Basic Information for CVE-2026-53502

Vulnerability Information
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Vulnerability Title
Thumbor has path traversal via post-validation URL decoding bypass in file_loader
Source: CVE Program / CVE List V5
Vulnerability Description
Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, file_loader decodes percent-encoded path segments after its root-boundary validation, allowing traversal outside FILE_LOADER_ROOT_PATH through watermark or frame filter input. This issue is fixed in 7.8.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5
Vulnerability Title
thumbor 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
thumbor thumbor是thumbor组织开源的一个图像处理服务。 thumbor 7.8.0之前版本存在路径遍历漏洞，该漏洞源于file_loader在根边界验证后解码百分号编码的路径段，可通过watermark或frame filter输入进行路径遍历，导致访问FILE_LOADER_ROOT_PATH之外的文件。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
thumbor thumbor < 7.8.0 -

II. Public POCs for CVE-2026-53502

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Qwen3.6-35B-A3B · 15733 chars
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Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
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III. Intelligence Information for CVE-2026-53502

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Patches & Fixes for CVE-2026-53502 (2)

Vendor Advisories for CVE-2026-53502 (1)

Same Patch Batch · thumbor · 2026-07-31 · 6 CVEs total

CVE-2026-53500 8.2 HIGH Thumbor treats ALLOWED_SOURCES string patterns as unescaped regex, allowing hostname bypas
CVE-2026-53501 8.2 HIGH Thumbor has HMAC validation bypass via multiple .replace() calls when removing URL signatu
CVE-2026-53505 7.5 HIGH Thumbor proportion filter allows unbounded post-transform resize leading to remote DoS
CVE-2026-53503 7.5 HIGH Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS
CVE-2026-53504 7.5 HIGH Thumbor has Regex Denial of Service (ReDoS) in `convolution` filter

IV. Related Vulnerabilities

Same product: thumbor
Same vendor: thumbor
Same weakness: CWE-22

V. Comments for CVE-2026-53502

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