--- id: "CVE-2026-87045" page: "https://infrastack.ai/live/CVE-2026-87045" kind: "vulnerability" aliases: ["CVE-2026-87045"] title: "Zephyr HTTP/2 server: stray CONTINUATION frame causes NULL pointer write and halts the device" severity: "high" cvss: 7.5 epss: null exploited: false status: "open" category: "runtime" products: [{"name": "zephyr", "fixed": ["4.3.2", "4.5.0"], "affected": ">= 4.1.0, < 4.3.2; >= 4.4.0, < 4.5.0", "ecosystem": "vendor"}] ecosystems: [] tags: ["embedded", "http2", "iot", "runtime", "unauthenticated", "zephyr"] not_affected_if: ["default-config", "http-server-disabled", "no-http-server", "no-http2"] published_at: "2026-11-06T15:17:26+00:00" first_seen_at: "2026-11-06T15:42:45+00:00" updated_at: "2026-11-06T15:44:52+00:00" sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-87045", "first_seen_at": "2026-11-06T15:42:45+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-11-06T15:44:52+00:00"}] exploit_sources: [] --- # Zephyr HTTP/2 server: stray CONTINUATION frame causes NULL pointer write and halts the device Link for people: https://infrastack.ai/live/CVE-2026-87045 (this .md is for agents) The Zephyr HTTP/2 server clears its stream binding on every frame, so a stray CONTINUATION frame with no preceding HEADERS makes a 404/405 response or a dynamic POST/PUT/PATCH write through a NULL pointer. An unauthenticated remote peer can fault and halt the device; the advisory states no confidentiality or integrity impact. _Summary, check and fix written by a model from the sources; labelled as such._ ## Affected - vendor:zephyr affected >= 4.1.0, < 4.3.2; >= 4.4.0, < 4.5.0 fixed 4.3.2, 4.5.0 ## How to check - Check whether your build sets CONFIG_HTTP_SERVER=y (HTTP/2 is built in, cleartext h2c accepted). Without it you are not affected. - Check your Zephyr version: affected are >= 4.1.0, < 4.3.2 and >= 4.4.0, < 4.5.0. Older than 4.1.0 is not listed as affected. ## Fix Upgrade Zephyr to 4.3.2 (4.1-4.3 line) or 4.5.0 (4.4 line); fix commit e72a9d9498092bfbb7feed4b479bf21bc3218c3d. Release lines without the backport remain affected. ## Timeline - 2026-11-06T15:42:45+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-87045 - 2026-11-06T15:44:52+00:00 analyst — Read Zephyr GHSA-cw8r-2jj2-w8fw and fix commit e72a9d9. Affected >=4.1.0,<4.3.2 and >=4.4.0,<4.5.0; fixed 4.3.2, 4.5.0. No workaround stated in advisory; not exploited/PoC not seen. Did not search social. ## Documents - [advisory] Vendor advisory: github.com https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-cw8r-2jj2-w8fw - [fix] Patch: github.com https://github.com/zephyrproject-rtos/zephyr/commit/e72a9d9498092bfbb7feed4b479bf21bc3218c3d ## From the sources The HTTP/2 server in subsys/net/lib/http/http_server_http2.c clears the connection's stream binding at the start of every frame. handle_http_frame_header() executed client->current_stream = NULL unconditionally, but a CONTINUATION frame does not open a new stream and enter_http_frame_continuation_state() never re-bound one, so the rest of the header block was processed with client->current_stream unset. Two paths then write through the NULL pointer. A request for an unregistered resource, or a method the matched resource does not support, is answered by send_http2_404() or send_http2_405(), and both call send_headers_frame(), which unconditionally sets client->current_stream->headers_sent = true. A POST, PUT or PATCH to a registered dynamic resource reaches handle_http2_dynamic_resource(), which unlike its siblings (handle_http2_static_resource(), dynamic_get_del_opts_req_v2(), dynamic_post_put_req_v2()) had no client->current_stream == NULL guard, and stores through the pointer with client->current_stream->current_detail = dynamic_detail. Any peer that can reach the server can trigger this without authentication or prior state. A single stray CONTINUATION frame with END_HEADERS set, sent right after the client preface and requesting any unregistered path, is enough, because nothing rejected a CONTINUATION that no HEADERS frame had opened. A legitimate split header block (a HEADERS frame with END_HEADERS clear whose payload ends on a header-field boundary, then a CONTINUATION with END_HEADERS set) reaches the same state. The in-tree test test_http2_post_headers_with_continuation() did not catch this because it splits the header block mid field, which takes the handle_incomplete_http_header() shortcut that keeps the stream bound. The result is a write to a fixed low address (a small offset into struct http2_stream_ctx), which faults on mainstream targets (flash/vector-table region on Cortex-M, or a trap under MPU/MMU null-pointer detection), and the default fatal-error handler halts the system. Impact is an unauthenticated, remotely triggerable denial of service against any device running the HTTP/2 server: the 404 path needs no particular resource to be registered, and HTTP/2 is built into CONFIG_HTTP_SERVER with cleartext h2c accepted, so TLS does not prevent it. Neither the target address nor the written value is attacker-controlled, so there is no confidentiality or integrity impact. Applications built without CONFIG_HTTP_SERVER are not affected. --- _Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_