CVE-2026-30871 OpenWrt Project has Stack-based Buffer Overflow in DNS PTR Query
A stack-based buffer overflow in OpenWrt's mdns daemon allows remote attackers to execute arbitrary code or cause denial of service via crafted DNS PTR queries.
- 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-2026-30871?
CVE-2026-30871 is a critical memory corruption vulnerability in Openwrt Openwrt, published on 19 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
OpenWrt Project is a Linux operating system targeting embedded devices. In versions prior to 24.10.6 and 25.12.1, the mdns daemon has a Stack-based Buffer Overflow vulnerability in the parse_question function. The issue is triggered by PTR queries for reverse DNS domains (.in-addr.arpa and .ip6.arpa). DNS packets received on UDP port 5353 are expanded by dn_expand into an 8096-byte global buffer (name_buffer), which is then copied via an unbounded strcpy into a fixed 256-byte stack buffer when handling TYPE_PTR queries. The overflow is possible because dn_expand converts non-printable ASCII bytes (e.g., 0x01) into multi-character octal representations (e.g., \001), significantly inflating the expanded name beyond the stack buffer's capacity. A crafted DNS packet can exploit this expansion behavior to overflow the stack buffer, making the vulnerability reachable through normal multicast DNS packet processing. This issue has been fixed in versions 24.10.6 and 25.12.1.
Weakness: CWE-121
Which versions are affected by CVE-2026-30871?
It affects 1 product.
Products include Openwrt Openwrt.
How do I fix CVE-2026-30871?
No fix has been published for CVE-2026-30871 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-30871 being exploited?
There is no known exploitation of CVE-2026-30871 in the wild and no public exploit code.
Other vulnerabilities in Openwrt Openwrt
Sources
Also known as GHSA-7c3j-f7w2-p8f6.