{"id":"CVE-2026-53503","aliases":["DEBIAN-CVE-2026-53503","EUVD-2026-51609","GHSA-cqjp-jf4r-h5q9","PYSEC-2026-3619","UBUNTU-CVE-2026-53503"],"status":"published","title":"Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS","description":"Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e) filter passes the user-controlled \u003ccolumns\u003e value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns \u003e 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.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.0075,"percentile":0.55253,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-20","CWE-369"],"published":"2026-07-31T18:54:20Z","modified":"2026-10-28T11:16:55Z","fixes":[{"ecosystem":"PyPI","package":"thumbor","fixed_in":["7.8.0"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:14","package":"thumbor","fixed_in":["7.8.0-1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"thumbor","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"7.7.7"},{"fixed":"7.8.0"}]}]},{"source":"osv","ecosystem":"Debian:14","package":"thumbor","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.8.0-1"}]}],"versions":["6.3.2-3","6.3.2-4","6.5.1-1","6.5.1-2","6.5.1-3","6.5.1-4","6.5.1-5","6.5.1-6","6.5.1-7","6.7.0-1","7.7.7-1","7.7.7-2","7.7.7-3","7.7.7-4","7.7.7-5","7.7.7-6"]},{"source":"osv","ecosystem":"PyPI","package":"thumbor","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.8.0"}]}],"versions":["4.1.3","4.10.0","4.10.1","4.10.2","4.10.3","4.11.0","4.11.1","4.12.0","4.12.1","4.12.2","4.4.1","4.5.3","4.5.4","4.6.0","4.7.0","4.7.1","4.8.0","4.8.1","4.8.2","4.8.3","4.8.4","4.8.5","4.8.6","4.9.0","4.9.1","5.0.0","5.0.0rc1","5.0.0rc2","5.0.1","5.0.2","5.0.3","5.0.4","5.0.5","5.0.6","5.1.0","5.2.0","5.2.1","6.0.0","6.0.0b1","6.0.0b2","6.0.0b3","6.0.0b4","6.0.0b5","6.0.1","6.0.2","6.1.0","6.1.1","6.1.2","6.1.3","6.1.4","6.1.5","6.2.0","6.2.1","6.3.0","6.3.1","6.3.2","6.4.0","6.4.1","6.4.2","6.4.3","6.5.0","6.5.1","6.5.2","6.6.0","6.6.1","6.7.0","6.7.1","6.7.2","6.7.3","6.7.4","6.7.5","6.7.6","7.0.0","7.0.0a1","7.0.0a2","7.0.0a3","7.0.0a4","7.0.0a5","7.0.0b1","7.0.1","7.0.10","7.0.11","7.0.12","7.0.2","7.0.3","7.0.5","7.0.6","7.0.7","7.0.8","7.0.9","7.1.0","7.1.1","7.1.2","7.2.0","7.2.1","7.3.0","7.3.1","7.3.2","7.4.0","7.4.1","7.4.2","7.4.3","7.4.4","7.4.5","7.4.6","7.4.7","7.5.0","7.5.1","7.5.2","7.6.0","7.7.0","7.7.1","7.7.2","7.7.3","7.7.4","7.7.5","7.7.6","7.7.7"]},{"source":"osv","ecosystem":"PyPI","package":"thumbor","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.8.0"}]}],"versions":["4.1.3","4.10.0","4.10.1","4.10.2","4.10.3","4.11.0","4.11.1","4.12.0","4.12.1","4.12.2","4.4.1","4.5.3","4.5.4","4.6.0","4.7.0","4.7.1","4.8.0","4.8.1","4.8.2","4.8.3","4.8.4","4.8.5","4.8.6","4.9.0","4.9.1","5.0.0","5.0.0rc1","5.0.0rc2","5.0.1","5.0.2","5.0.3","5.0.4","5.0.5","5.0.6","5.1.0","5.2.0","5.2.1","6.0.0","6.0.0b1","6.0.0b2","6.0.0b3","6.0.0b4","6.0.0b5","6.0.1","6.0.2","6.1.0","6.1.1","6.1.2","6.1.3","6.1.4","6.1.5","6.2.0","6.2.1","6.3.0","6.3.1","6.3.2","6.4.0","6.4.1","6.4.2","6.4.3","6.5.0","6.5.1","6.5.2","6.6.0","6.6.1","6.7.0","6.7.1","6.7.2","6.7.3","6.7.4","6.7.5","6.7.6","7.0.0","7.0.0a1","7.0.0a2","7.0.0a3","7.0.0a4","7.0.0a5","7.0.0b1","7.0.1","7.0.10","7.0.11","7.0.12","7.0.2","7.0.3","7.0.5","7.0.6","7.0.7","7.0.8","7.0.9","7.1.0","7.1.1","7.1.2","7.2.0","7.2.1","7.3.0","7.3.1","7.3.2","7.4.0","7.4.1","7.4.2","7.4.3","7.4.4","7.4.5","7.4.6","7.4.7","7.5.0","7.5.1","7.5.2","7.6.0","7.7.0","7.7.1","7.7.2","7.7.3","7.7.4","7.7.5","7.7.6","7.7.7"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"thumbor","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["7.7.7-4","7.7.7-5"]}],"products":[{"vendor":"thumbor","product":"thumbor"}],"references":[{"url":"https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9","tags":["x_refsource_CONFIRM","exploit","advisory","web","report"]},{"url":"https://github.com/thumbor/thumbor/commit/447e192e3fb92e64c12e5354a56a4a7133f69d73","tags":["x_refsource_MISC","fix","web","report"]},{"url":"https://github.com/thumbor/thumbor/releases/tag/7.8.0","tags":["x_refsource_MISC","web","report"]},{"url":"https://github.com/advisories/GHSA-cqjp-jf4r-h5q9","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53503.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53503","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-53503","tags":["advisory"]},{"url":"https://github.com/thumbor/thumbor","tags":["package"]},{"url":"https://pypi.org/project/thumbor","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2026-53503","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-53503","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-53503","title":"Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS","description":"Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e) filter passes the user-controlled \u003ccolumns\u003e value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns \u003e 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.","status":"published","published":"2026-07-31T18:54:20.747Z","modified":"2026-07-31T21:39:35.108Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-20","CWE-369"],"updated_at":"2026-11-02T14:20:00.11477Z"}],"euvd":[{"id":"EUVD-2026-51609","description":"Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e) filter passes the user-controlled \u003ccolumns\u003e value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns \u003e 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.","status":"published","published":"2026-07-31T18:54:20Z","modified":"2026-07-31T21:39:35Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T18:02:25.159179Z"}],"ghsa":[{"id":"GHSA-cqjp-jf4r-h5q9","title":"Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS","description":"### Summary\nThumbor's `filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e)` filter passes the user-controlled `\u003ccolumns\u003e` value to a C extension (`thumbor/ext/filters/_convolution.c`) where it is used as a divisor (for `%` and `/`) without validating `columns \u003e 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 (confirmed on Linux x86_64 and macOS Intel x86_64), causing a remote denial of service.\n\n### Details\n#### Root cause\nThe Python filter accepts `columns=0`, and the native C extension uses `columns_count` as a divisor without validating it.\n\n1) Python filter entry point allows `columns=0` (`thumbor/filters/convolution.py`):\n```python\n@filter_method(\n    r\"(?:[-]?[\\d]+\\.?[\\d]*[;])*(?:[-]?[\\d]+\\.?[\\d]*)\",\n    BaseFilter.PositiveNumber,  # accepts 0\n    BaseFilter.Boolean,\n)\nasync def convolution(self, matrix, columns, should_normalize=True):\n    ...\n    imgdata = _convolution.apply(..., matrix, columns, should_normalize)\n```\n`BaseFilter.PositiveNumber` matches `\"0\"` (`thumbor/filters/__init__.py`):\n```python\nclass BaseFilter:\n    PositiveNumber = {\"regex\": r\"[\\d]+\", \"parse\": int}  # matches \"0\"\n    PositiveNonZeroNumber = {\"regex\": r\"[\\d]*[1-9][\\d]*\", \"parse\": int}\n```\n\n2) C extension divides/modulos by `columns_count` without a zero check (`thumbor/ext/filters/_convolution.c`):\n```c\nkernel_size = PyTuple_Size(kernel_tuple);\nif ((kernel_size % columns_count != 0) ||\n    (kernel_size % 2 == 0) ||\n    ((kernel_size / columns_count) % 2) == 0) {\n    // TODO: error, not a valid kernel\n    return NULL;\n}\n```\n\n\n### PoC\n#### Test environment\n- Linux x86_64\n\n#### Preconditions\n- The `convolution` filter is enabled (it is enabled by default via `BUILTIN_FILTERS`).\n- Either:\n  - `/unsafe/` URLs are allowed (`ALLOW_UNSAFE_URL=True`), OR\n  - `/unsafe/` is disabled, and the attacker has a valid signed URL (i.e., the attacker is an authorized user/partner, or can obtain signed URLs from a trusted signing service).\n\n#### Example request (signed URL)\n`http://\u003chost\u003e:\u003cport\u003e/\u003curl-sign\u003e/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg`\n\n#### Example request (/unsafe/)\n`http://\u003chost\u003e:\u003cport\u003e/unsafe/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg`\n\n\n### Impact\n- Remote Denial of Service via process crash (SIGFPE) on x86_64 (confirmed on Linux x86_64 and macOS Intel x86_64).\n- Exploitability depends on deployment:\n  - If `/unsafe/` is enabled: unauthenticated remote DoS.\n  - If `/unsafe/` is disabled: the attacker needs a valid signed URL.(i.e., the attacker is an authorized user/partner, or can obtain signed URLs from a trusted signing service)\n\n\n### Suggested remediation\n- In the C extension (`thumbor/ext/filters/_convolution.c`):\n  - Reject `columns_count \u003c= 0` before any `%` or `/`.\n- In the Python filter (`thumbor/filters/convolution.py`):\n  - Require `columns` to be non-zero (e.g., use `BaseFilter.PositiveNonZeroNumber`).","status":"published","published":"2026-07-31T18:54:55Z","modified":"2026-07-31T18:54:57Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-20","CWE-369"],"updated_at":"2026-11-02T14:40:55.903445Z"}],"nvd":[{"id":"CVE-2026-53503","description":"Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e) filter passes the user-controlled \u003ccolumns\u003e value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns \u003e 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.","status":"published","published":"2026-07-31T19:17:09.737Z","modified":"2026-09-08T20:51:43.49Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-20","CWE-369"],"updated_at":"2026-11-02T14:12:34.290716Z"}],"osv":[{"id":"CVE-2026-53503","title":"Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS","description":"Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e) filter passes the user-controlled \u003ccolumns\u003e value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns \u003e 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.","status":"published","published":"2026-07-31T18:54:20.747Z","modified":"2026-10-28T11:16:55.892856862Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-20","CWE-369"],"updated_at":"2026-11-02T15:45:08.132336Z"},{"id":"DEBIAN-CVE-2026-53503","description":"Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e) filter passes the user-controlled \u003ccolumns\u003e value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns \u003e 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.","status":"published","published":"2026-07-31T19:17:09.737Z","modified":"2026-10-01T03:03:18.891385253Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:45:57.236551Z"},{"id":"GHSA-cqjp-jf4r-h5q9","title":"Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS","description":"### Summary\nThumbor's `filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e)` filter passes the user-controlled `\u003ccolumns\u003e` value to a C extension (`thumbor/ext/filters/_convolution.c`) where it is used as a divisor (for `%` and `/`) without validating `columns \u003e 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 (confirmed on Linux x86_64 and macOS Intel x86_64), causing a remote denial of service.\n\n### Details\n#### Root cause\nThe Python filter accepts `columns=0`, and the native C extension uses `columns_count` as a divisor without validating it.\n\n1) Python filter entry point allows `columns=0` (`thumbor/filters/convolution.py`):\n```python\n@filter_method(\n    r\"(?:[-]?[\\d]+\\.?[\\d]*[;])*(?:[-]?[\\d]+\\.?[\\d]*)\",\n    BaseFilter.PositiveNumber,  # accepts 0\n    BaseFilter.Boolean,\n)\nasync def convolution(self, matrix, columns, should_normalize=True):\n    ...\n    imgdata = _convolution.apply(..., matrix, columns, should_normalize)\n```\n`BaseFilter.PositiveNumber` matches `\"0\"` (`thumbor/filters/__init__.py`):\n```python\nclass BaseFilter:\n    PositiveNumber = {\"regex\": r\"[\\d]+\", \"parse\": int}  # matches \"0\"\n    PositiveNonZeroNumber = {\"regex\": r\"[\\d]*[1-9][\\d]*\", \"parse\": int}\n```\n\n2) C extension divides/modulos by `columns_count` without a zero check (`thumbor/ext/filters/_convolution.c`):\n```c\nkernel_size = PyTuple_Size(kernel_tuple);\nif ((kernel_size % columns_count != 0) ||\n    (kernel_size % 2 == 0) ||\n    ((kernel_size / columns_count) % 2) == 0) {\n    // TODO: error, not a valid kernel\n    return NULL;\n}\n```\n\n\n### PoC\n#### Test environment\n- Linux x86_64\n\n#### Preconditions\n- The `convolution` filter is enabled (it is enabled by default via `BUILTIN_FILTERS`).\n- Either:\n  - `/unsafe/` URLs are allowed (`ALLOW_UNSAFE_URL=True`), OR\n  - `/unsafe/` is disabled, and the attacker has a valid signed URL (i.e., the attacker is an authorized user/partner, or can obtain signed URLs from a trusted signing service).\n\n#### Example request (signed URL)\n`http://\u003chost\u003e:\u003cport\u003e/\u003curl-sign\u003e/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg`\n\n#### Example request (/unsafe/)\n`http://\u003chost\u003e:\u003cport\u003e/unsafe/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg`\n\n\n### Impact\n- Remote Denial of Service via process crash (SIGFPE) on x86_64 (confirmed on Linux x86_64 and macOS Intel x86_64).\n- Exploitability depends on deployment:\n  - If `/unsafe/` is enabled: unauthenticated remote DoS.\n  - If `/unsafe/` is disabled: the attacker needs a valid signed URL.(i.e., the attacker is an authorized user/partner, or can obtain signed URLs from a trusted signing service)\n\n\n### Suggested remediation\n- In the C extension (`thumbor/ext/filters/_convolution.c`):\n  - Reject `columns_count \u003c= 0` before any `%` or `/`.\n- In the Python filter (`thumbor/filters/convolution.py`):\n  - Require `columns` to be non-zero (e.g., use `BaseFilter.PositiveNonZeroNumber`).","status":"published","published":"2026-07-31T18:54:55Z","modified":"2026-08-04T14:41:06.639351419Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-20","CWE-369"],"updated_at":"2026-11-02T15:46:45.28161Z"},{"id":"PYSEC-2026-3619","title":"Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS","description":"### Summary\nThumbor's `filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e)` filter passes the user-controlled `\u003ccolumns\u003e` value to a C extension (`thumbor/ext/filters/_convolution.c`) where it is used as a divisor (for `%` and `/`) without validating `columns \u003e 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 (confirmed on Linux x86_64 and macOS Intel x86_64), causing a remote denial of service.\n\n### Details\n#### Root cause\nThe Python filter accepts `columns=0`, and the native C extension uses `columns_count` as a divisor without validating it.\n\n1) Python filter entry point allows `columns=0` (`thumbor/filters/convolution.py`):\n```python\n@filter_method(\n    r\"(?:[-]?[\\d]+\\.?[\\d]*[;])*(?:[-]?[\\d]+\\.?[\\d]*)\",\n    BaseFilter.PositiveNumber,  # accepts 0\n    BaseFilter.Boolean,\n)\nasync def convolution(self, matrix, columns, should_normalize=True):\n    ...\n    imgdata = _convolution.apply(..., matrix, columns, should_normalize)\n```\n`BaseFilter.PositiveNumber` matches `\"0\"` (`thumbor/filters/__init__.py`):\n```python\nclass BaseFilter:\n    PositiveNumber = {\"regex\": r\"[\\d]+\", \"parse\": int}  # matches \"0\"\n    PositiveNonZeroNumber = {\"regex\": r\"[\\d]*[1-9][\\d]*\", \"parse\": int}\n```\n\n2) C extension divides/modulos by `columns_count` without a zero check (`thumbor/ext/filters/_convolution.c`):\n```c\nkernel_size = PyTuple_Size(kernel_tuple);\nif ((kernel_size % columns_count != 0) ||\n    (kernel_size % 2 == 0) ||\n    ((kernel_size / columns_count) % 2) == 0) {\n    // TODO: error, not a valid kernel\n    return NULL;\n}\n```\n\n\n### PoC\n#### Test environment\n- Linux x86_64\n\n#### Preconditions\n- The `convolution` filter is enabled (it is enabled by default via `BUILTIN_FILTERS`).\n- Either:\n  - `/unsafe/` URLs are allowed (`ALLOW_UNSAFE_URL=True`), OR\n  - `/unsafe/` is disabled, and the attacker has a valid signed URL (i.e., the attacker is an authorized user/partner, or can obtain signed URLs from a trusted signing service).\n\n#### Example request (signed URL)\n`http://\u003chost\u003e:\u003cport\u003e/\u003curl-sign\u003e/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg`\n\n#### Example request (/unsafe/)\n`http://\u003chost\u003e:\u003cport\u003e/unsafe/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg`\n\n\n### Impact\n- Remote Denial of Service via process crash (SIGFPE) on x86_64 (confirmed on Linux x86_64 and macOS Intel x86_64).\n- Exploitability depends on deployment:\n  - If `/unsafe/` is enabled: unauthenticated remote DoS.\n  - If `/unsafe/` is disabled: the attacker needs a valid signed URL.(i.e., the attacker is an authorized user/partner, or can obtain signed URLs from a trusted signing service)\n\n\n### Suggested remediation\n- In the C extension (`thumbor/ext/filters/_convolution.c`):\n  - Reject `columns_count \u003c= 0` before any `%` or `/`.\n- In the Python filter (`thumbor/filters/convolution.py`):\n  - Require `columns` to be non-zero (e.g., use `BaseFilter.PositiveNonZeroNumber`).","status":"published","published":"2026-08-04T11:34:46.338544Z","modified":"2026-08-04T14:30:17.900502764Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:56.847083Z"},{"id":"UBUNTU-CVE-2026-53503","description":"Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor's filters:convolution(\u003cmatrix\u003e, \u003ccolumns\u003e, \u003cshould_normalize\u003e) filter passes the user-controlled \u003ccolumns\u003e value to a C extension (thumbor/ext/filters/_convolution.c) where it is used as a divisor (for % and /) without validating columns \u003e 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.","status":"published","published":"2026-07-31T19:17:00Z","modified":"2026-08-06T00:20:53Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T16:56:41.382716Z"}]}}