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vuln-cve/data/2026/82xxx/CVE-2026-82391.json
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{
"dataType": "CVE_RECORD",
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"cveMetadata": {
"cveId": "CVE-2026-82391",
"assignerOrgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"state": "PUBLISHED",
"assignerShortName": "zephyr",
"dateReserved": "2026-08-28T21:11:46.166Z",
"datePublished": "2026-11-10T22:07:39.047Z",
"dateUpdated": "2026-11-13T13:36:09.236Z"
},
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"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"shortName": "zephyr",
"dateUpdated": "2026-11-10T22:07:39.047Z"
},
"title": "Out-of-bounds write in Zephyr HTTP/2 server static-filesystem handler via corrupted receive-buffer length",
"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."
}
],
"affected": [
{
"vendor": "zephyrproject",
"product": "zephyr",
"collectionURL": "https://github.com/zephyrproject-rtos/zephyr",
"packageName": "zephyr",
"defaultStatus": "unaffected",
"programFiles": [
"subsys/net/lib/http/http_server_http2.c"
],
"programRoutines": [
{
"name": "handle_http2_static_fs_resource"
}
],
"versions": [
{
"version": "4.0.0",
"status": "affected",
"versionType": "semver",
"lessThan": "4.3.2"
},
{
"version": "4.4.0",
"status": "affected",
"versionType": "semver",
"lessThan": "4.5.0"
}
]
}
],
"references": [
{
"url": "https://github.com/zephyrproject-rtos/zephyr/commit/4e0a5f38b14dba5891fb558c49a526f9f6a3cc29",
"name": "Fix commit",
"tags": [
"patch"
]
},
{
"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-8jrg-wx88-g75j",
"name": "GHSA-8jrg-wx88-g75j"
}
],
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"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"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"lang": "en",
"description": "memory-safety",
"cweId": "CWE-787",
"type": "CWE"
}
]
}
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"engine": "cvelib 1.8.0"
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"content": {
"timestamp": "2026-11-13T13:35:55.858780Z",
"id": "CVE-2026-82391",
"options": [
{
"Exploitation": "none"
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"Automatable": "yes"
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"role": "CISA Coordinator",
"version": "2.0.3"
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"title": "CISA ADP Vulnrichment",
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"dateUpdated": "2026-11-13T13:36:09.236Z"
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