---
id: CVE-2026-10652
title: >-
  Zephyr's DNS resolver (subsys/net/lib/dns) parses resource records from DNS
  responses in dns_unpack_answer(), which validated only the fixed RR header
  (type, class, TTL, rdlength) and accepted any attacker-declared rdlength,
  including on…
summary: >-
  Zephyr's DNS resolver (subsys/net/lib/dns) parses resource records from DNS
  responses in dns_unpack_answer(), which validated only the fixed RR header
  (type, class, TTL, rdlength) and accepted any attacker-declared rdlength,
  including on…
severity: medium
cvss: 4.8
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L'
cwe:
  - CWE-125
vendor: zephyrproject
product: zephyr
affected:
  - 'zephyr >= 4.3.0, <= 4.4.1'
published: '2026-06-30'
updated: '2026-07-17'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-10652'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/58b46c81c6796dac4dc7391f32ba006474f94dc8
    label: vulnerabilities@zephyrproject.org
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-3jxq-xx8g-q8j2
    label: vulnerabilities@zephyrproject.org
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-3jxq-xx8g-q8j2
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.00415
epssPercentile: 0.355
ingestedAt: '2026-07-18T13:23:33.088Z'
---

## Overview

Zephyr's DNS resolver (subsys/net/lib/dns) parses resource records from DNS responses in dns_unpack_answer(), which validated only the fixed RR header (type, class, TTL, rdlength) and accepted any attacker-declared rdlength, including one extending past the end of the received datagram. The TXT and SRV consumers in dns_validate_record() (resolve.c) then read up to rdlength bytes (clamped only to a record-type maximum such as DNS_MAX_TEXT_SIZE, default 64, not to the packet) from the receive buffer via memcpy without their own bounds check, and pass the result to the application's resolve callback. A malicious or spoofed DNS server, an on-path attacker forging UDP DNS replies, or (with mDNS/LLMNR enabled) any LAN node can craft a truncated TXT or SRV response that causes an out-of-bounds read of adjacent receive-pool memory; the disclosed stale bytes (residual contents of prior DNS packets / uninitialized pool memory) are returned to the application as TXT/SRV record contents, an information leak, and may in some configurations cross the allocation boundary and fault, causing a denial of service. The read is bounded (~64 bytes for TXT, ~6 for SRV) and read-only (no write). The fix rejects any record whose declared rdata extends past dns_msg->msg_size at the single chokepoint in dns_unpack_answer(). Affected: v4.3.0 and v4.4.0.

## Affected

- `zephyr >= 4.3.0, <= 4.4.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.