{"id":"CVE-2026-53502","aliases":["DEBIAN-CVE-2026-53502","EUVD-2026-51612","GHSA-cj54-hpcc-gj6h","PYSEC-2026-3618","UBUNTU-CVE-2026-53502"],"status":"published","title":"Thumbor has path traversal via post-validation URL decoding bypass in file_loader","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.","severity":{"version":"4.0","score":8.7,"vector":"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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00522,"percentile":0.44671,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-22"],"published":"2026-07-31T19:03:16Z","modified":"2026-10-28T02:30:56Z","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-cj54-hpcc-gj6h","tags":["x_refsource_CONFIRM","exploit","advisory","web","report"]},{"url":"https://github.com/thumbor/thumbor/commit/3b986d13677b30fe6651c8c72ebb25957ac0a40d","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-cj54-hpcc-gj6h","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53502.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53502","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-53502","tags":["advisory"]},{"url":"https://github.com/thumbor/thumbor","tags":["package"]},{"url":"https://pypi.org/project/thumbor","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2026-53502","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-53502","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-53502","title":"Thumbor has path traversal via post-validation URL decoding bypass in file_loader","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.","status":"published","published":"2026-07-31T19:03:16.522Z","modified":"2026-07-31T19:18:09.047Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high","assessor":"cna"}],"cwes":["CWE-22"],"updated_at":"2026-11-02T14:20:00.11477Z"}],"euvd":[{"id":"EUVD-2026-51612","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.","status":"published","published":"2026-07-31T19:03:16Z","modified":"2026-07-31T19:18:09Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"updated_at":"2026-11-02T18:02:25.522444Z"}],"ghsa":[{"id":"GHSA-cj54-hpcc-gj6h","title":"Thumbor has path traversal via post-validation URL decoding bypass in file_loader","description":"The file_loader performs `unquote()` on the file path AFTER the `abspath() + startswith()` security check. An attacker can use percent-encoded path traversal sequences (`%2e%2e` for `..`) that pass the security check as literal directory names, but are then decoded to actual `..` traversal sequences.\n\n## Affected code\n\n`thumbor/loaders/file_loader.py` lines 28-49:\n```python\nasync def load(context, path):\n    file_path = join(\n        context.config.FILE_LOADER_ROOT_PATH.rstrip(\"/\"), path.lstrip(\"/\")\n    )\n    file_path = abspath(file_path)\n    inside_root_path = file_path.startswith(         # Security check\n        abspath(context.config.FILE_LOADER_ROOT_PATH)\n    )\n    result = LoaderResult()\n    if not inside_root_path:\n        result.error = LoaderResult.ERROR_NOT_FOUND\n        result.successful = False\n        return result\n\n    if not exists(file_path):\n        file_path = unquote(file_path)               # unquote AFTER check!\n\n    if exists(file_path) and isfile(file_path):\n        with open(file_path, \"rb\") as source_file:\n            ...\n```\n\nThe watermark and frame filters pass their URL parameters directly to the loader without re-encoding (unlike the main image URL flow which applies `quote()` in `imaging.py` line 37).\n\n## PoC\n\n```bash\n# Read /etc/passwd via watermark filter path traversal\n# %252e is double-encoded: Tornado decodes to %2e, filter passes to file_loader,\n# file_loader unquote decodes %2e to .\ncurl 'http://thumbor-host:8888/unsafe/filters:watermark(%252e%252e/%252e%252e/%252e%252e/%252e%252e/etc/passwd,0,0,100)/some-valid-image.jpg'\n```\n\nFlow:\n1. `%252e%252e` arrives at Tornado, decoded to `%2e%2e`\n2. Watermark filter passes `%2e%2e/%2e%2e/.../etc/passwd` to file_loader\n3. `join(ROOT, '%2e%2e/...')` = `ROOT/%2e%2e/...`\n4. `abspath()` sees `%2e%2e` as literal dir name (no dots to resolve)\n5. `startswith(ROOT)` = True (passes check)\n6. `exists()` returns False (literal `%2e%2e` dir doesn't exist)\n7. `unquote()` converts `%2e%2e` to `..`\n8. OS resolves `..` → reads files outside ROOT\n\n## Prerequisites\n\n- `LOADER = thumbor.loaders.file_loader` (or `file_loader_http_fallback`)\n- `ALLOW_UNSAFE_URL = True` (this is the default)\n- watermark/frame filters are enabled by default (in BUILTIN_FILTERS)\n\n## Impact\n\nArbitrary file read on the thumbor server. When the file is a valid image format, its content is returned in the response overlaid as a watermark. Can be used to read configuration files, secrets, private keys, etc.","status":"published","published":"2026-07-31T19:03:54Z","modified":"2026-07-31T19:03:55Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"cwes":["CWE-22"],"updated_at":"2026-11-02T14:40:55.903445Z"}],"nvd":[{"id":"CVE-2026-53502","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.","status":"published","published":"2026-07-31T19:17:09.577Z","modified":"2026-09-08T20:51:43.49Z","cvss":[{"version":"4.0","score":8.7,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"}],"cwes":["CWE-22"],"updated_at":"2026-11-02T14:12:34.290716Z"}],"osv":[{"id":"CVE-2026-53502","title":"Thumbor has path traversal via post-validation URL decoding bypass in file_loader","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.","status":"published","published":"2026-07-31T19:03:16.522Z","modified":"2026-10-28T02:30:56.073451727Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"cwes":["CWE-22"],"updated_at":"2026-11-02T15:45:08.132336Z"},{"id":"DEBIAN-CVE-2026-53502","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.","status":"published","published":"2026-07-31T19:17:09.577Z","modified":"2026-10-01T03:03:18.89102777Z","cvss":[{"version":"4.0","score":8.7,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"}],"updated_at":"2026-11-02T15:45:57.236551Z"},{"id":"GHSA-cj54-hpcc-gj6h","title":"Thumbor has path traversal via post-validation URL decoding bypass in file_loader","description":"The file_loader performs `unquote()` on the file path AFTER the `abspath() + startswith()` security check. An attacker can use percent-encoded path traversal sequences (`%2e%2e` for `..`) that pass the security check as literal directory names, but are then decoded to actual `..` traversal sequences.\n\n## Affected code\n\n`thumbor/loaders/file_loader.py` lines 28-49:\n```python\nasync def load(context, path):\n    file_path = join(\n        context.config.FILE_LOADER_ROOT_PATH.rstrip(\"/\"), path.lstrip(\"/\")\n    )\n    file_path = abspath(file_path)\n    inside_root_path = file_path.startswith(         # Security check\n        abspath(context.config.FILE_LOADER_ROOT_PATH)\n    )\n    result = LoaderResult()\n    if not inside_root_path:\n        result.error = LoaderResult.ERROR_NOT_FOUND\n        result.successful = False\n        return result\n\n    if not exists(file_path):\n        file_path = unquote(file_path)               # unquote AFTER check!\n\n    if exists(file_path) and isfile(file_path):\n        with open(file_path, \"rb\") as source_file:\n            ...\n```\n\nThe watermark and frame filters pass their URL parameters directly to the loader without re-encoding (unlike the main image URL flow which applies `quote()` in `imaging.py` line 37).\n\n## PoC\n\n```bash\n# Read /etc/passwd via watermark filter path traversal\n# %252e is double-encoded: Tornado decodes to %2e, filter passes to file_loader,\n# file_loader unquote decodes %2e to .\ncurl 'http://thumbor-host:8888/unsafe/filters:watermark(%252e%252e/%252e%252e/%252e%252e/%252e%252e/etc/passwd,0,0,100)/some-valid-image.jpg'\n```\n\nFlow:\n1. `%252e%252e` arrives at Tornado, decoded to `%2e%2e`\n2. Watermark filter passes `%2e%2e/%2e%2e/.../etc/passwd` to file_loader\n3. `join(ROOT, '%2e%2e/...')` = `ROOT/%2e%2e/...`\n4. `abspath()` sees `%2e%2e` as literal dir name (no dots to resolve)\n5. `startswith(ROOT)` = True (passes check)\n6. `exists()` returns False (literal `%2e%2e` dir doesn't exist)\n7. `unquote()` converts `%2e%2e` to `..`\n8. OS resolves `..` → reads files outside ROOT\n\n## Prerequisites\n\n- `LOADER = thumbor.loaders.file_loader` (or `file_loader_http_fallback`)\n- `ALLOW_UNSAFE_URL = True` (this is the default)\n- watermark/frame filters are enabled by default (in BUILTIN_FILTERS)\n\n## Impact\n\nArbitrary file read on the thumbor server. When the file is a valid image format, its content is returned in the response overlaid as a watermark. Can be used to read configuration files, secrets, private keys, etc.","status":"published","published":"2026-07-31T19:03:54Z","modified":"2026-08-04T14:40:39.499145349Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"cwes":["CWE-22"],"updated_at":"2026-11-02T15:46:45.28161Z"},{"id":"PYSEC-2026-3618","title":"Thumbor has path traversal via post-validation URL decoding bypass in file_loader","description":"The file_loader performs `unquote()` on the file path AFTER the `abspath() + startswith()` security check. An attacker can use percent-encoded path traversal sequences (`%2e%2e` for `..`) that pass the security check as literal directory names, but are then decoded to actual `..` traversal sequences.\n\n## Affected code\n\n`thumbor/loaders/file_loader.py` lines 28-49:\n```python\nasync def load(context, path):\n    file_path = join(\n        context.config.FILE_LOADER_ROOT_PATH.rstrip(\"/\"), path.lstrip(\"/\")\n    )\n    file_path = abspath(file_path)\n    inside_root_path = file_path.startswith(         # Security check\n        abspath(context.config.FILE_LOADER_ROOT_PATH)\n    )\n    result = LoaderResult()\n    if not inside_root_path:\n        result.error = LoaderResult.ERROR_NOT_FOUND\n        result.successful = False\n        return result\n\n    if not exists(file_path):\n        file_path = unquote(file_path)               # unquote AFTER check!\n\n    if exists(file_path) and isfile(file_path):\n        with open(file_path, \"rb\") as source_file:\n            ...\n```\n\nThe watermark and frame filters pass their URL parameters directly to the loader without re-encoding (unlike the main image URL flow which applies `quote()` in `imaging.py` line 37).\n\n## PoC\n\n```bash\n# Read /etc/passwd via watermark filter path traversal\n# %252e is double-encoded: Tornado decodes to %2e, filter passes to file_loader,\n# file_loader unquote decodes %2e to .\ncurl 'http://thumbor-host:8888/unsafe/filters:watermark(%252e%252e/%252e%252e/%252e%252e/%252e%252e/etc/passwd,0,0,100)/some-valid-image.jpg'\n```\n\nFlow:\n1. `%252e%252e` arrives at Tornado, decoded to `%2e%2e`\n2. Watermark filter passes `%2e%2e/%2e%2e/.../etc/passwd` to file_loader\n3. `join(ROOT, '%2e%2e/...')` = `ROOT/%2e%2e/...`\n4. `abspath()` sees `%2e%2e` as literal dir name (no dots to resolve)\n5. `startswith(ROOT)` = True (passes check)\n6. `exists()` returns False (literal `%2e%2e` dir doesn't exist)\n7. `unquote()` converts `%2e%2e` to `..`\n8. OS resolves `..` → reads files outside ROOT\n\n## Prerequisites\n\n- `LOADER = thumbor.loaders.file_loader` (or `file_loader_http_fallback`)\n- `ALLOW_UNSAFE_URL = True` (this is the default)\n- watermark/frame filters are enabled by default (in BUILTIN_FILTERS)\n\n## Impact\n\nArbitrary file read on the thumbor server. When the file is a valid image format, its content is returned in the response overlaid as a watermark. Can be used to read configuration files, secrets, private keys, etc.","status":"published","published":"2026-08-04T11:34:46.521252Z","modified":"2026-08-04T14:30:17.840498063Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"updated_at":"2026-11-02T15:52:56.847083Z"},{"id":"UBUNTU-CVE-2026-53502","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.","status":"published","published":"2026-07-31T19:17:00Z","modified":"2026-08-06T00:20:53Z","cvss":[{"version":"4.0","score":8.7,"vector":"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","level":"high"}],"updated_at":"2026-11-02T16:56:41.382716Z"}]}}