{"id":"CVE-2026-54571","state":"PUBLISHED","title":"ESPAsyncWebServer: Integer overflow in multipart boundary parser causes denial of service","description":"ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. Prior to 3.11.1, the multipart/form-data parser in src/WebRequest.cpp stores _boundaryPosition as an 8-bit value while _parseMultipartPostByte processes the boundary. A remote request containing an exactly 256-byte multipart boundary wraps _boundaryPosition from 255 to zero, prevents the boundary parsing loop from terminating, consumes excessive CPU, and triggers a FreeRTOS watchdog reset on affected ESP32 or ESP8266 devices. This issue is fixed in version 3.11.1.","publishedAt":"2026-09-17T18:28:26.977Z","updatedAt":"2026-09-21T21:05:49.373Z","severity":{"score":8.7,"label":"High","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["ESP32Async ESPAsyncWebServer"],"affected":[{"vendor":"ESP32Async","product":"ESPAsyncWebServer","versions":[{"version":"< 3.11.1","status":"affected"}]}],"references":["https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-4phx-fcj6-46r4","https://github.com/ESP32Async/ESPAsyncWebServer/pull/445","https://github.com/ESP32Async/ESPAsyncWebServer/commit/b928de7cbd7debcd6266ece6a6c46f10a86d3a6f","https://github.com/ESP32Async/ESPAsyncWebServer/releases/tag/v3.11.1"],"weaknesses":["CWE-190"],"ingestedAt":"2026-10-29T20:12:24.861Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/54xxx/CVE-2026-54571.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-54571","state":"PUBLISHED","datePublished":"2026-09-17T18:28:26.977Z","dateUpdated":"2026-09-21T21:05:49.373Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-06-15T19:15:27.343Z"},"containers":{"cna":{"title":"ESPAsyncWebServer: Integer overflow in multipart boundary parser causes denial of service","descriptions":[{"lang":"en","value":"ESPAsyncWebServer is an asynchronous HTTP and WebSocket server library for ESP32, ESP8266, RP2040 and RP2350. Prior to 3.11.1, the multipart/form-data parser in src/WebRequest.cpp stores _boundaryPosition as an 8-bit value while _parseMultipartPostByte processes the boundary. A remote request containing an exactly 256-byte multipart boundary wraps _boundaryPosition from 255 to zero, prevents the boundary parsing loop from terminating, consumes excessive CPU, and triggers a FreeRTOS watchdog reset on affected ESP32 or ESP8266 devices. This issue is fixed in version 3.11.1."}],"affected":[{"vendor":"ESP32Async","product":"ESPAsyncWebServer","versions":[{"version":"< 3.11.1","status":"affected"}]}],"references":[{"url":"https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-4phx-fcj6-46r4","name":"https://github.com/ESP32Async/ESPAsyncWebServer/security/advisories/GHSA-4phx-fcj6-46r4","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/ESP32Async/ESPAsyncWebServer/pull/445","name":"https://github.com/ESP32Async/ESPAsyncWebServer/pull/445","tags":["x_refsource_MISC"]},{"url":"https://github.com/ESP32Async/ESPAsyncWebServer/commit/b928de7cbd7debcd6266ece6a6c46f10a86d3a6f","name":"https://github.com/ESP32Async/ESPAsyncWebServer/commit/b928de7cbd7debcd6266ece6a6c46f10a86d3a6f","tags":["x_refsource_MISC"]},{"url":"https://github.com/ESP32Async/ESPAsyncWebServer/releases/tag/v3.11.1","name":"https://github.com/ESP32Async/ESPAsyncWebServer/releases/tag/v3.11.1","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":8.7,"baseSeverity":"HIGH","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-190","lang":"en","description":"CWE-190: Integer Overflow or Wraparound","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-09-17T18:28:26.977Z"},"source":{"advisory":"GHSA-4phx-fcj6-46r4","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-21T21:05:35.710251Z","id":"CVE-2026-54571","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-21T21:05:49.373Z"}}]}}}