CVE-2026-10652 Out-of-bounds read in Zephyr DNS resolver TXT/SRV record parsing (unvalidated `rdlength`)
A malicious DNS server can trigger an out-of-bounds read in Zephyr's resolver, leaking memory contents or causing a crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-10652?
CVE-2026-10652 is a medium-severity vulnerability in Zephyrproject Zephyr, published on 30 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-125
Which versions are affected by CVE-2026-10652?
It affects 1 product.
Products include Zephyrproject Zephyr.
How do I fix CVE-2026-10652?
No fix has been published for CVE-2026-10652 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-10652 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-10652 exists.
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Sources
Also known as GHSA-3jxq-xx8g-q8j2.