# 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.

- **Severity:** Critical 9.5 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Mar 2026
- **Updated:** 25 Mar 2026
- **Also known as:** GHSA-7c3j-f7w2-p8f6

## 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 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-30871?

It affects 1 product.


Products: 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.

## 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

- [CVE-2020-28951](https://insights.sbomify.com/CVE-2020-28951/): Use after free in n/a (critical 9.8)
- [CVE-2026-62948](https://insights.sbomify.com/CVE-2026-62948/): Cross-site scripting in openwrt (critical 9.6)
- [CVE-2026-30872](https://insights.sbomify.com/CVE-2026-30872/): OpenWrt Project has a Stack-based Buffer Overflow vulnerability via IPv6 reverse DNS lookup (critical 9.5)
- [CVE-2021-28961](https://insights.sbomify.com/CVE-2021-28961/): Command injection in n/a (high 8.8)
- [CVE-2019-17367](https://insights.sbomify.com/CVE-2019-17367/): Cross-site request forgery in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-30871 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-30871 in the wild and no public exploit code.

Affected product: Openwrt Openwrt. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-30871/ (Markdown: https://insights.sbomify.com/CVE-2026-30871/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-30871
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-30871
- OSV: https://osv.dev/vulnerability/CVE-2026-30871

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-30871/
Summaries are generated and may contain mistakes; the official description above is the record.