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CVE-2026-53503— Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS

CVSS 7.5 · High EPSS 0.42% · P34

Possible ATT&CK Techniques 1AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProductVersion RangeStatus
thumborthumbor< 7.8.0affected
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I. Basic Information for CVE-2026-53503

Vulnerability Information
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Vulnerability Title
Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
thumbor 输入验证错误漏洞
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之前版本存在安全漏洞，该漏洞源于convolution过滤器将用户控制的columns值用作除数且未验证其大于0，可能导致除零错误并造成进程崩溃，远程拒绝服务。
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

VendorProductAffected VersionsCPESubscribe
thumborthumbor < 7.8.0 -

II. Public POCs for CVE-2026-53503

#POC DescriptionSource LinkShenlong Link
AI-Generated POCPremium
Qwen3.6-35B-A3B · 6434 chars
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III. Intelligence Information for CVE-2026-53503

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Patches & Fixes for CVE-2026-53503 (2)

Vendor Advisories for CVE-2026-53503 (1)

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

CVE-2026-535028.7 HIGHThumbor has path traversal via post-validation URL decoding bypass in file_loader
CVE-2026-535008.2 HIGHThumbor treats ALLOWED_SOURCES string patterns as unescaped regex, allowing hostname bypas
CVE-2026-535018.2 HIGHThumbor has HMAC validation bypass via multiple .replace() calls when removing URL signatu
CVE-2026-535057.5 HIGHThumbor proportion filter allows unbounded post-transform resize leading to remote DoS
CVE-2026-535047.5 HIGHThumbor has Regex Denial of Service (ReDoS) in `convolution` filter

IV. Related Vulnerabilities

Same product: thumbor
Same vendor: thumbor
Same weakness: CWE-20

V. Comments for CVE-2026-53503

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