{"api_version":"1","generated_at":"2026-11-10T23:06:03+00:00","cve":"CVE-2026-82391","urls":{"html":"https://cve.report/CVE-2026-82391","api":"https://cve.report/api/cve/CVE-2026-82391.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-82391","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-82391"},"summary":{"title":"Out-of-bounds write in Zephyr HTTP/2 server static-filesystem handler via corrupted receive-buffer length","description":"The HTTP/2 front-end of the Zephyr HTTP server aliased connection receive state as a scratch output. In subsys/net/lib/http/http_server_http2.c, handle_http2_static_fs_resource() passed &client->data_len as the file_size out-parameter of http_server_find_file(). client->data_len is the count of unprocessed bytes remaining in the fixed-size per-connection receive buffer client->buffer[CONFIG_HTTP_SERVER_CLIENT_BUFFER_SIZE] (256 bytes by default), an invariant every frame handler and the socket receive path rely on. Serving any static file therefore replaced that bounded value with the file's on-disk size, and nothing resets it afterwards.\n\nThe defect is reached by an unauthenticated HTTP/2 GET for any file under the web root, in applications that register a static-filesystem resource (HTTP_RESOURCE_TYPE_STATIC_FS) with CONFIG_FILE_SYSTEM=y; CONFIG_HTTP_SERVER_VERSION_2 is enabled by default and no TLS or credentials are required on this path. Once client->data_len exceeds the buffer size, the frame dispatch loop in subsys/net/lib/http/http_server_core.c keeps parsing past the end of the received data, and the peer controls the bytes at client->cursor, so it can choose which fabricated frame the state machine consumes next by appending bytes after its request.\n\nThe inflated length defeats the only guards on the buffer. parse_http_frame_header() and the per-frame handlers read and skip up to a 24-bit frame length beyond the buffer (out-of-bounds read); the compaction memmove(client->buffer, client->cursor, client->data_len) at the end of request handling copies the file-size number of bytes into the 256-byte buffer, overflowing the rest of struct http_client_ctx — including the current_detail/current_stream pointers, the parser_settings function-pointer table and the inactivity_timer work handler — and the adjacent client contexts in static memory; and the subsequent zsock_recv(client->fd, client->buffer + client->data_len, sizeof(client->buffer) - client->data_len, 0) underflows its size argument, writing attacker-supplied data of attacker-chosen length out of bounds.\n\nThe impact is remote memory corruption in the server's single address space: at minimum a crash or hang of the device, and plausibly control-data overwrite leading to code execution. The HTTP/1 and HTTP/3 static-filesystem handlers already used a local variable and are unaffected; the fix makes the HTTP/2 handler use a local size_t file_size as well.","state":"PUBLISHED","assigner":"zephyr","published_at":"2026-11-10 22:21:05","updated_at":"2026-11-10 22:21:05"},"problem_types":["CWE-787","CWE-787 memory-safety"],"metrics":[{"version":"3.1","source":"vulnerabilities@zephyrproject.org","type":"Secondary","score":"9.1","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","baseScore":9.1,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"CVSS","score":"9.1","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","data":{"baseScore":9.1,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8jrg-wx88-g75j","name":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8jrg-wx88-g75j","refsource":"vulnerabilities@zephyrproject.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/zephyrproject-rtos/zephyr/commit/4e0a5f38b14dba5891fb558c49a526f9f6a3cc29","name":"https://github.com/zephyrproject-rtos/zephyr/commit/4e0a5f38b14dba5891fb558c49a526f9f6a3cc29","refsource":"vulnerabilities@zephyrproject.org","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-82391","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-82391","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"zephyrproject","product":"zephyr","version":"affected 4.0.0 4.3.2 semver","platforms":[]},{"source":"CNA","vendor":"zephyrproject","product":"zephyr","version":"affected 4.4.0 4.5.0 semver","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"collectionURL":"https://github.com/zephyrproject-rtos/zephyr","defaultStatus":"unaffected","packageName":"zephyr","product":"zephyr","programFiles":["subsys/net/lib/http/http_server_http2.c"],"programRoutines":[{"name":"handle_http2_static_fs_resource"}],"vendor":"zephyrproject","versions":[{"lessThan":"4.3.2","status":"affected","version":"4.0.0","versionType":"semver"},{"lessThan":"4.5.0","status":"affected","version":"4.4.0","versionType":"semver"}]}],"descriptions":[{"lang":"en","value":"The HTTP/2 front-end of the Zephyr HTTP server aliased connection receive state as a scratch output. In subsys/net/lib/http/http_server_http2.c, handle_http2_static_fs_resource() passed &client->data_len as the file_size out-parameter of http_server_find_file(). client->data_len is the count of unprocessed bytes remaining in the fixed-size per-connection receive buffer client->buffer[CONFIG_HTTP_SERVER_CLIENT_BUFFER_SIZE] (256 bytes by default), an invariant every frame handler and the socket receive path rely on. Serving any static file therefore replaced that bounded value with the file's on-disk size, and nothing resets it afterwards.\n\nThe defect is reached by an unauthenticated HTTP/2 GET for any file under the web root, in applications that register a static-filesystem resource (HTTP_RESOURCE_TYPE_STATIC_FS) with CONFIG_FILE_SYSTEM=y; CONFIG_HTTP_SERVER_VERSION_2 is enabled by default and no TLS or credentials are required on this path. Once client->data_len exceeds the buffer size, the frame dispatch loop in subsys/net/lib/http/http_server_core.c keeps parsing past the end of the received data, and the peer controls the bytes at client->cursor, so it can choose which fabricated frame the state machine consumes next by appending bytes after its request.\n\nThe inflated length defeats the only guards on the buffer. parse_http_frame_header() and the per-frame handlers read and skip up to a 24-bit frame length beyond the buffer (out-of-bounds read); the compaction memmove(client->buffer, client->cursor, client->data_len) at the end of request handling copies the file-size number of bytes into the 256-byte buffer, overflowing the rest of struct http_client_ctx — including the current_detail/current_stream pointers, the parser_settings function-pointer table and the inactivity_timer work handler — and the adjacent client contexts in static memory; and the subsequent zsock_recv(client->fd, client->buffer + client->data_len, sizeof(client->buffer) - client->data_len, 0) underflows its size argument, writing attacker-supplied data of attacker-chosen length out of bounds.\n\nThe impact is remote memory corruption in the server's single address space: at minimum a crash or hang of the device, and plausibly control-data overwrite leading to code execution. The HTTP/1 and HTTP/3 static-filesystem handlers already used a local variable and are unaffected; the fix makes the HTTP/2 handler use a local size_t file_size as well."}],"metrics":[{"cvssV3_1":{"baseScore":9.1,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-787","description":"memory-safety","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-11-10T22:07:39.047Z","orgId":"e2e69745-5e70-4e92-8431-deb5529a81ad","shortName":"zephyr"},"references":[{"name":"Fix commit","tags":["patch"],"url":"https://github.com/zephyrproject-rtos/zephyr/commit/4e0a5f38b14dba5891fb558c49a526f9f6a3cc29"},{"name":"GHSA-8jrg-wx88-g75j","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8jrg-wx88-g75j"}],"title":"Out-of-bounds write in Zephyr HTTP/2 server static-filesystem handler via corrupted receive-buffer length","x_generator":{"engine":"cvelib 1.8.0"}}},"cveMetadata":{"assignerOrgId":"e2e69745-5e70-4e92-8431-deb5529a81ad","assignerShortName":"zephyr","cveId":"CVE-2026-82391","datePublished":"2026-11-10T22:07:39.047Z","dateReserved":"2026-08-28T21:11:46.166Z","dateUpdated":"2026-11-10T22:07:39.047Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-11-10 22:21:05","lastModifiedDate":"2026-11-10 22:21:05","problem_types":["CWE-787","CWE-787 memory-safety"],"metrics":{"cvssMetricV31":[{"source":"vulnerabilities@zephyrproject.org","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","baseScore":9.1,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.2}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"82391","Ordinal":"1","Title":"Out-of-bounds write in Zephyr HTTP/2 server static-filesystem ha","CVE":"CVE-2026-82391","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"82391","Ordinal":"1","NoteData":"The HTTP/2 front-end of the Zephyr HTTP server aliased connection receive state as a scratch output. In subsys/net/lib/http/http_server_http2.c, handle_http2_static_fs_resource() passed &client->data_len as the file_size out-parameter of http_server_find_file(). client->data_len is the count of unprocessed bytes remaining in the fixed-size per-connection receive buffer client->buffer[CONFIG_HTTP_SERVER_CLIENT_BUFFER_SIZE] (256 bytes by default), an invariant every frame handler and the socket receive path rely on. Serving any static file therefore replaced that bounded value with the file's on-disk size, and nothing resets it afterwards.\n\nThe defect is reached by an unauthenticated HTTP/2 GET for any file under the web root, in applications that register a static-filesystem resource (HTTP_RESOURCE_TYPE_STATIC_FS) with CONFIG_FILE_SYSTEM=y; CONFIG_HTTP_SERVER_VERSION_2 is enabled by default and no TLS or credentials are required on this path. Once client->data_len exceeds the buffer size, the frame dispatch loop in subsys/net/lib/http/http_server_core.c keeps parsing past the end of the received data, and the peer controls the bytes at client->cursor, so it can choose which fabricated frame the state machine consumes next by appending bytes after its request.\n\nThe inflated length defeats the only guards on the buffer. parse_http_frame_header() and the per-frame handlers read and skip up to a 24-bit frame length beyond the buffer (out-of-bounds read); the compaction memmove(client->buffer, client->cursor, client->data_len) at the end of request handling copies the file-size number of bytes into the 256-byte buffer, overflowing the rest of struct http_client_ctx — including the current_detail/current_stream pointers, the parser_settings function-pointer table and the inactivity_timer work handler — and the adjacent client contexts in static memory; and the subsequent zsock_recv(client->fd, client->buffer + client->data_len, sizeof(client->buffer) - client->data_len, 0) underflows its size argument, writing attacker-supplied data of attacker-chosen length out of bounds.\n\nThe impact is remote memory corruption in the server's single address space: at minimum a crash or hang of the device, and plausibly control-data overwrite leading to code execution. The HTTP/1 and HTTP/3 static-filesystem handlers already used a local variable and are unaffected; the fix makes the HTTP/2 handler use a local size_t file_size as well.","Type":"Description","Title":"Out-of-bounds write in Zephyr HTTP/2 server static-filesystem ha"}]}}}