# CVE-2026-87045: NULL pointer dereference in the Zephyr HTTP/2 server when a header block is completed by a CONTINUATION frame

Status: published. Published: 2026-11-06. Updated: 2026-11-10.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: zephyr) — https://github.com/zephyrproject-rtos/zephyr/commit/e72a9d9498092bfbb7feed4b479bf21bc3218c3d
- fix: zephyr (other): GitHub reports patched versions 4.3.2. Check the advisory for the affected release branch. (source: GitHub GHSA-cw8r-2jj2-w8fw) — https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-cw8r-2jj2-w8fw
- fix: zephyr (other): GitHub reports patched versions 4.5.0. Check the advisory for the affected release branch. (source: GitHub GHSA-cw8r-2jj2-w8fw) — https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-cw8r-2jj2-w8fw

## Affected products and versions

- zephyrproject / zephyr (zephyr): ≥ 4.1.0; < 4.3.2 (affected, semver); ≥ 4.4.0; < 4.5.0 (affected, semver). Source: CNA: zephyr
-  / zephyr (zephyr): >= 4.1.0, < 4.3.2 (affected, GitHub advisory range). Source: GitHub GHSA-cw8r-2jj2-w8fw
-  / zephyr (zephyr): >= 4.4.0, < 4.5.0 (affected, GitHub advisory range). Source: GitHub GHSA-cw8r-2jj2-w8fw

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: zephyr

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: vulnerabilities@zephyrproject.org

- CISA KEV: No listing in collected sources

- EPSS: 0.38% as of 2026-11-10; percentile 32.56%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-476

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/e72a9d9498092bfbb7feed4b479bf21bc3218c3d (CNA: zephyr; patch)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-cw8r-2jj2-w8fw (CNA: zephyr)

- https://github.com/zephyrproject-rtos/zephyr/commit/e72a9d9498092bfbb7feed4b479bf21bc3218c3d (vulnerabilities@zephyrproject.org)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-cw8r-2jj2-w8fw (vulnerabilities@zephyrproject.org)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-cw8r-2jj2-w8fw (GitHub Security Advisories; advisory)

## Provenance

- CNA: zephyr: https://www.cve.org/CVERecord?id=CVE-2026-87045; retrieved 2026-11-10; source updated 2026-11-10

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-87045; retrieved 2026-11-06; source updated 2026-11-06

- GitHub Security Advisories: https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-cw8r-2jj2-w8fw; retrieved 2026-11-08; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-87045; retrieved 2026-11-10; source updated Not reported

Revision: f44027b446e990976e033d249e89d29735096c784ef438f588a11596a39dbdb2

Canonical: https://y2.dev/cve/CVE-2026-87045

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.