dbcve.org
OpenwrtOperating system

CVE-2026-30872

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-19
Fix available
A fix is available. Upgrade to 24.10.6 / 25.12.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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 match_ipv6_addresses function, triggered when processing PTR queries for IPv6 reverse DNS domains (.ip6.arpa) received via multicast DNS on UDP port 5353. During processing, the domain name from name_buffer is copied via strcpy into a fixed 256-byte stack buffer, and then the reverse IPv6 request is extracted into a buffer of only 46 bytes (INET6_ADDRSTRLEN). Because the length of the data is never validated before this extraction, an attacker can supply input larger than 46 bytes, causing an out-of-bounds write. This allows a specially crafted DNS query to overflow the stack buffer in match_ipv6_addresses, potentially enabling remote code execution. This issue has been fixed in versions 24.10.6 and 25.12.1.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Stack-based buffer overflow in the mdns daemon's match_ipv6_addresses function. When processing PTR queries for IPv6 reverse DNS domains (.ip6.arpa) received via multicast DNS on UDP port 5353, the code copies domain name data using strcpy into a fixed 256-byte stack buffer, then extracts the reverse IPv6 request into a 46-byte buffer (INET6_ADDRSTRLEN) without validating input length. An attacker can supply more than 46 bytes, causing an out-of-bounds write and potentially achieving remote code execution.

MitigationUpgrade to OpenWrt versions 24.10.6 or 25.12.1 which contain the patch. If immediate upgrade is not possible, disable the mDNS daemon or block UDP port 5353 at the network perimeter to prevent external attackers from reaching the vulnerable service.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
OpenwrtOperating system
Affected:< 24.10.6>= 25.12.0, < 25.12.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm OpenWrt is the running system
    Check /etc/os-release or run 'cat /etc/os-release' to verify the operating system identifies as OpenWrt
    Affected if The system is not running OpenWrt (this CVE only affects OpenWrt)
  2. Check installed OpenWrt version
    Run 'cat /etc/os-release' and look for the VERSION or VERSION_ID field, or use 'opkg list-installed base-files' to get the exact version number
    Affected if Version is less than 24.10.6, OR between 25.12.0 and 25.12.1 (inclusive of 25.12.0 and exclusive of 25.12.1)
  3. Verify mdns daemon is enabled
    Run '/etc/init.d/mdns status' or check for the mdns process with 'ps | grep mdns'
    Affected if The mdns daemon process is running or enabled (the vulnerability only triggers when mdns is active)
  4. Check if UDP port 5353 is listening
    Run 'netstat -ulnp | grep 5353' or 'ss -ulnp | grep 5353' to see if the mDNS service is bound to UDP port 5353
    Affected if UDP port 5353 is open and listening (this is the attack vector for receiving malicious PTR queries)

You are affected if your OpenWrt version falls within the vulnerable ranges AND the mdns daemon is running with UDP port 5353 exposed to potential attackers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 24.10.6 / 25.12.1 or later
Fixed in 24.10.625.12.1
Interim mitigation

Upgrade to OpenWrt versions 24.10.6 or 25.12.1 which contain the patch. If immediate upgrade is not possible, disable the mDNS daemon or block UDP port 5353 at the network perimeter to prevent external attackers from reaching the vulnerable service.

Recommended fix High confidence

OpenWrt 24.10.6 or later for the 24.x stable branch; OpenWrt 25.12.1 or later for the 25.x stable branch

  1. Backup current OpenWrt configuration using sysupgrade -b /tmp/backup.tar.gz
  2. Download the appropriate fixed firmware image for your device from the official OpenWrt downloads page (https://downloads.openwrt.org/)
  3. Verify the firmware checksum (SHA256) matches the official release
  4. Upload the firmware through the LuCI web interface System > Backup/Flash Operations > Flash new firmware, or use CLI: sysupgrade -v /tmp/firmware.bin
  5. Ensure stable power during the flash process and allow the device to fully reboot
  6. After reboot, restore configuration if needed: sysupgrade -r /tmp/backup.tar.gz
  7. Verify the mdns package version is updated and the vulnerability is patched
Caveat Upgrading OpenWrt firmware may introduce changes to default settings, package compatibility, or require reconfiguration of custom scripts; review release notes before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Openwrt Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-30872 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data