Vulnerability-Lookup

PYSEC-2026-3619

Vulnerability from pysec - Published: 2026-08-04 11:34 - Updated: 2026-08-04 13:36

Details

Summary

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 (confirmed on Linux x86_64 and macOS Intel x86_64), causing a remote denial of service.

Details

Root cause

The Python filter accepts columns=0, and the native C extension uses columns_count as a divisor without validating it.

1) Python filter entry point allows columns=0 (thumbor/filters/convolution.py):

@filter_method(
    r"(?:[-]?[\d]+\.?[\d]*[;])*(?:[-]?[\d]+\.?[\d]*)",
    BaseFilter.PositiveNumber,  # accepts 0
    BaseFilter.Boolean,
)
async def convolution(self, matrix, columns, should_normalize=True):
    ...
    imgdata = _convolution.apply(..., matrix, columns, should_normalize)

BaseFilter.PositiveNumber matches "0" (thumbor/filters/__init__.py):

class BaseFilter:
    PositiveNumber = {"regex": r"[\d]+", "parse": int}  # matches "0"
    PositiveNonZeroNumber = {"regex": r"[\d]*[1-9][\d]*", "parse": int}

2) C extension divides/modulos by columns_count without a zero check (thumbor/ext/filters/_convolution.c):

kernel_size = PyTuple_Size(kernel_tuple);
if ((kernel_size % columns_count != 0) ||
    (kernel_size % 2 == 0) ||
    ((kernel_size / columns_count) % 2) == 0) {
    // TODO: error, not a valid kernel
    return NULL;
}

PoC

Test environment

Linux x86_64

Preconditions

The convolution filter is enabled (it is enabled by default via BUILTIN_FILTERS).
Either:
/unsafe/ URLs are allowed (ALLOW_UNSAFE_URL=True), OR
/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).

Example request (signed URL)

http://<host>:<port>/<url-sign>/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg

Example request (/unsafe/)

http://<host>:<port>/unsafe/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg

Impact

Remote Denial of Service via process crash (SIGFPE) on x86_64 (confirmed on Linux x86_64 and macOS Intel x86_64).
Exploitability depends on deployment:
If /unsafe/ is enabled: unauthenticated remote DoS.
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)

Suggested remediation

In the C extension (thumbor/ext/filters/_convolution.c):
Reject columns_count <= 0 before any % or /.
In the Python filter (thumbor/filters/convolution.py):
Require columns to be non-zero (e.g., use BaseFilter.PositiveNonZeroNumber).

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Impacted products

Name	purl
thumbor	pkg:pypi/thumbor

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "thumbor",
        "purl": "pkg:pypi/thumbor"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.8.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "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"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-53503",
    "GHSA-cqjp-jf4r-h5q9"
  ],
  "details": "### Summary\nThumbor\u0027s `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`).",
  "id": "PYSEC-2026-3619",
  "modified": "2026-08-04T13:36:38.176268Z",
  "published": "2026-08-04T11:34:46.338544Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9"
    },
    {
      "type": "WEB",
      "url": "https://github.com/thumbor/thumbor/commit/447e192e3fb92e64c12e5354a56a4a7133f69d73"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/thumbor/thumbor"
    },
    {
      "type": "WEB",
      "url": "https://github.com/thumbor/thumbor/releases/tag/7.8.0"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/thumbor"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-cqjp-jf4r-h5q9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53503"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS"
}

CVE-2026-53503 (GCVE-0-2026-53503)

Vulnerability from cvelistv5 – Published: 2026-07-31 18:54 – Updated: 2026-07-31 21:39

Title

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

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.

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-31 20:14 UTC

CWE

CWE-20 - Improper Input Validation
CWE-369 - Divide By Zero

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/thumbor/thumbor/security/advis…	x_refsource_CONFIRM
https://github.com/thumbor/thumbor/commit/447e192…	x_refsource_MISC
https://github.com/thumbor/thumbor/releases/tag/7.8.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
thumbor	thumbor	Affected: < 7.8.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-53503",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-31T20:14:06.472673Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-31T21:39:35.108Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "thumbor",
          "vendor": "thumbor",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 7.8.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, Thumbor\u0027s 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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-20",
              "description": "CWE-20: Improper Input Validation",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-369",
              "description": "CWE-369: Divide By Zero",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-31T18:54:20.747Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9"
        },
        {
          "name": "https://github.com/thumbor/thumbor/commit/447e192e3fb92e64c12e5354a56a4a7133f69d73",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/thumbor/thumbor/commit/447e192e3fb92e64c12e5354a56a4a7133f69d73"
        },
        {
          "name": "https://github.com/thumbor/thumbor/releases/tag/7.8.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/thumbor/thumbor/releases/tag/7.8.0"
        }
      ],
      "source": {
        "advisory": "GHSA-cqjp-jf4r-h5q9",
        "discovery": "UNKNOWN"
      },
      "title": "Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-53503",
    "datePublished": "2026-07-31T18:54:20.747Z",
    "dateReserved": "2026-06-09T17:05:25.059Z",
    "dateUpdated": "2026-07-31T21:39:35.108Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-CQJP-JF4R-H5Q9

Vulnerability from github – Published: 2026-07-31 18:54 – Updated: 2026-07-31 18:54

Summary

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

Details

Summary

Details

Root cause

The Python filter accepts columns=0, and the native C extension uses columns_count as a divisor without validating it.

1) Python filter entry point allows columns=0 (thumbor/filters/convolution.py):

@filter_method(
    r"(?:[-]?[\d]+\.?[\d]*[;])*(?:[-]?[\d]+\.?[\d]*)",
    BaseFilter.PositiveNumber,  # accepts 0
    BaseFilter.Boolean,
)
async def convolution(self, matrix, columns, should_normalize=True):
    ...
    imgdata = _convolution.apply(..., matrix, columns, should_normalize)

BaseFilter.PositiveNumber matches "0" (thumbor/filters/__init__.py):

class BaseFilter:
    PositiveNumber = {"regex": r"[\d]+", "parse": int}  # matches "0"
    PositiveNonZeroNumber = {"regex": r"[\d]*[1-9][\d]*", "parse": int}

2) C extension divides/modulos by columns_count without a zero check (thumbor/ext/filters/_convolution.c):

kernel_size = PyTuple_Size(kernel_tuple);
if ((kernel_size % columns_count != 0) ||
    (kernel_size % 2 == 0) ||
    ((kernel_size / columns_count) % 2) == 0) {
    // TODO: error, not a valid kernel
    return NULL;
}

PoC

Test environment

Linux x86_64

Preconditions

The convolution filter is enabled (it is enabled by default via BUILTIN_FILTERS).
Either:
/unsafe/ URLs are allowed (ALLOW_UNSAFE_URL=True), OR
/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).

Example request (signed URL)

http://<host>:<port>/<url-sign>/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg

Example request (/unsafe/)

http://<host>:<port>/unsafe/400x400/filters:convolution(1;2;1;2;4;2;1;2;1,0,true)/example.jpg

Impact

Remote Denial of Service via process crash (SIGFPE) on x86_64 (confirmed on Linux x86_64 and macOS Intel x86_64).
Exploitability depends on deployment:
If /unsafe/ is enabled: unauthenticated remote DoS.
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)

Suggested remediation

In the C extension (thumbor/ext/filters/_convolution.c):
Reject columns_count <= 0 before any % or /.
In the Python filter (thumbor/filters/convolution.py):
Require columns to be non-zero (e.g., use BaseFilter.PositiveNonZeroNumber).

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 7.7.7"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "thumbor"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.8.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-53503"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20",
      "CWE-369"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-31T18:54:55Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\nThumbor\u0027s `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`).",
  "id": "GHSA-cqjp-jf4r-h5q9",
  "modified": "2026-07-31T18:54:55Z",
  "published": "2026-07-31T18:54:55Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/thumbor/thumbor/security/advisories/GHSA-cqjp-jf4r-h5q9"
    },
    {
      "type": "WEB",
      "url": "https://github.com/thumbor/thumbor/commit/447e192e3fb92e64c12e5354a56a4a7133f69d73"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/thumbor/thumbor"
    },
    {
      "type": "WEB",
      "url": "https://github.com/thumbor/thumbor/releases/tag/7.8.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Thumbor convolution filter allows divide-by-zero in C extension leading to remote DoS"
}

Sightings

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Action not permitted

PYSEC-2026-3619

Summary

Details

Root cause

PoC

Test environment

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Example request (signed URL)

Example request (/unsafe/)

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CVE-2026-53503 (GCVE-0-2026-53503)

GHSA-CQJP-JF4R-H5Q9

Summary

Details

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PoC

Test environment

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Example request (signed URL)

Example request (/unsafe/)

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