CVE-2026-35579 CoreDNS TSIG authentication bypass on gRPC, QUIC, DoH, and DoH3 transports
Unauthenticated attackers can bypass TSIG authentication on gRPC, QUIC, DoH, and DoH3 transports to perform unauthorized zone transfers or DNS updates.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-35579?
CVE-2026-35579 is a high-severity authentication bypass vulnerability in coredns, published on 5 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-35579?
3 open source packages ship an affected version, including github.com/coredns/coredns. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/coredns/coredns Go | All versions | 1.14.3 |
github.com/coredns/coredns Go | All versions | 1.14.3 |
github.com/coredns/coredns Go | All versions | 1.14.3 |
Products include Coredns.io Coredns.
How do I fix CVE-2026-35579?
Upgrade github.com/coredns/coredns to 1.14.3 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-35579 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-35579 exists.
Other vulnerabilities in coredns
- CVE-2026-32934 CoreDNS DNS-over-QUIC unbounded goroutine growth leads to denial of service
- CVE-2026-32936 CoreDNS DoH GET path missing size validation causes CPU and memory amplification
- CVE-2026-33190 CoreDNS TSIG authentication bypass on encrypted DNS transports
- CVE-2026-33489 CoreDNS transfer plugin subzone ACL bypass via lexicographic zone comparison
- CVE-2026-26017 CoreDNS ACL Bypass
Sources
Also known as AZL-85730, CLEANSTART-2026-LE40219, CLEANSTART-2026-WT82281, ECHO-a028-dd5c-1ba5, GHSA-vp29-5652-4fw9, GO-2026-5667 and 25 more.