CVE-2026-35579
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk41th percentile - higher than 41% of all known CVEs
Summary
CoreDNS versions prior to 1.14.3 incorrectly handle TSIG authentication in gRPC, QUIC, DoH, and DoH3 transports. For gRPC and QUIC, the server only checks the TSIG key name but does not validate the HMAC, so any request with a matching key name is considered authenticated. For DoH and DoH3, the issue is more severe – the server never inspects the TSIG record at all, so any request with TSIG is treated as authenticated.
Risk Assessment
An unauthenticated network attacker can bypass TSIG protection and access features such as AXFR/IXFR zone transfers or dynamic DNS updates. For DoH and DoH3, the attack is easier because it does not require knowledge of a valid TSIG key name.
Recommendation
Upgrade CoreDNS to version 1.14.3. As a temporary workaround, disable gRPC, QUIC, DoH, and DoH3 listeners where TSIG authentication is required, or restrict network access to those ports to trusted sources only.
Original NVD description (English source)
CoreDNS is a DNS server written in Go. In versions prior to 1.14.3, the gRPC, QUIC, DoH, and DoH3 transport implementations incorrectly handle TSIG authentication. For gRPC and QUIC, the server checks whether the TSIG key name exists in the configuration but never calls dns.TsigVerify() to validate the HMAC. If the key name matches a configured key, the tsigStatus field remains nil and the tsig plugin treats the request as successfully authenticated regardless of the MAC value. For DoH and DoH3, the issue is more severe: the DoHWriter.TsigStatus() method unconditionally returns nil, and the server never inspects the TSIG record at all. Any request containing a TSIG record is treated as authenticated over DoH and DoH3, even if the key name is invalid and the MAC is arbitrary. An unauthenticated network attacker can exploit this to bypass TSIG-protected functionality such as AXFR/IXFR zone transfers, dynamic DNS updates, or other TSIG-gated plugin behavior. The DoH and DoH3 variants have a lower exploitation bar because the attacker does not need to know a valid TSIG key name. This issue has been fixed in version 1.14.3. As a workaround, disable gRPC, QUIC, DoH, and DoH3 listeners where TSIG authentication is required, or restrict network-level access to affected transport ports to trusted sources only.