Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| NLnet Labs | Unbound | unaffected |
|
| Package | CPE | Advisory | Released Date |
|---|---|---|---|
| Red Hat Hardened Images | |||
| unbound-main-1.25.2-0.1.hum1 | cpe:/a:redhat:hummingbird:1 | RHSA-2026:43588 | 2026-07-22T00:00:00Z |
| Vendor | Product | Versions | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Nlnetlabs | Unbound |
|
Vendor Solution
This issue is fixed starting with version 1.25.2
| Source | ID | Title |
|---|---|---|
Debian DSA |
DSA-6507-1 | unbound security update |
Ubuntu USN |
USN-8946-1 | Unbound vulnerabilities |
Ubuntu USN |
USN-8946-2 | Unbound vulnerabilities |
No CVSS v4.0
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.285% probability within 30 days)
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Redhat
Redhat hummingbird |
|
| Weaknesses | CWE-770 | |
| CPEs | cpe:/a:redhat:hummingbird:1 | |
| Vendors & Products |
Redhat
Redhat hummingbird |
|
| References |
| |
| Metrics |
threat_severity
|
threat_severity
|
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Nlnetlabs
Nlnetlabs unbound |
|
| Vendors & Products |
Nlnetlabs
Nlnetlabs unbound |
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
|
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and large input buffers are allocated later, after only the 2-byte length prefix has been received from the initial streams. As a result, a remote client can make Unbound exceed the configured 'quic-size' limit with low-cost input. Using only one connection and two streams, each sending a declared 65535-byte length prefix and then holding the streams open, a client can already trivially make Unbound roughly allocate double that amount. This is a remote availability issue / memory-accounting bypass in the downstream DoQ implementation that leads to denial of service for new DoQ clients. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces. | |
| Title | Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass | |
| Weaknesses | CWE-1284 | |
| References |
| |
| Metrics |
cvssV3_1
|