How severe is CVE-2026-30871?

CVE-2026-30871 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-30871 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (65th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-30871?

CVE-2026-30871 affects Openwrt. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-30871?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-30871 have an EU (EUVD) identifier?

Yes. CVE-2026-30871 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13247.

When was CVE-2026-30871 published?

CVE-2026-30871 was published on 2026-03-19 and last updated on 2026-06-17.

CVE-2026-30871

CVE-2026-30871 is a critical-severity vulnerability in Openwrt with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-121.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v4: 9.5
EPSS exploit prediction: 1% (65th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-13247
Weakness: CWE-121
Affected product: Openwrt
Published: 2026-03-19
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-30871?: 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.
How severe is CVE-2026-30871?: CVE-2026-30871 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-30871 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (65th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-30871?: CVE-2026-30871 affects Openwrt. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-30871?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-30871 have an EU (EUVD) identifier?: Yes. CVE-2026-30871 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13247.
When was CVE-2026-30871 published?: CVE-2026-30871 was published on 2026-03-19 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:o:openwrt:openwrt:*:*:*:*:*:*:*:*

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