In NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as datstart + dname_valid(datstart, …) and passes it straight to query_dname_tolower() without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause query_dname_tolower() to walk label-by-label through stale bytes in the per-worker env->scratch_buffer, past the end of that heap allocation if msg-buffer-size has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.
Weakness
The product does not validate or incorrectly validates the integrity check values or “checksums” of a message. This may prevent it from detecting if the data has been modified or corrupted in transmission.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Unbound | Ubuntu | upstream | * |
Potential Mitigations
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/145.html
- https://cwe.mitre.org/data/definitions/463.html
- https://cwe.mitre.org/data/definitions/75.html