CVE-2026-82399 CoreDNS: Unauthenticated memory exhaustion in custom transports
Unauthenticated attackers can exhaust memory via crafted DNS-over-HTTPS/QUIC/gRPC requests, causing CoreDNS to crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-82399?
CVE-2026-82399 is a high-severity denial of service vulnerability in coredns, published on 16 Sep 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. Prior to 1.14.7, the DNS-over-HTTPS, DNS-over-HTTP/3, DNS-over-QUIC, and DNS-over-gRPC request paths in plugin/pkg/doh/doh.go, core/dnsserver/server_quic.go, and core/dnsserver/server_grpc.go call dns.Msg.Unpack on attacker-controlled DNS section counts before dns.DefaultMsgAcceptFunc validates the fixed header. An unauthenticated client can use DNS name compression and excessive section counts to amplify allocation before the plugin chain, so plugin-level rate limiting cannot prevent concurrent requests from exhausting memory and terminating CoreDNS. The ordinary UDP and TCP listeners are not affected because they validate the header first. This issue is fixed in version 1.14.7.
Weakness: CWE-770
Which versions are affected by CVE-2026-82399?
3 open source packages ship an affected version, including github.com/coredns/coredns.
| Package | Affected | Fixed in |
|---|---|---|
github.com/coredns/coredns Go | All versions | 1.14.7 |
github.com/coredns/coredns Go | All versions | 1.14.7 |
github.com/coredns/coredns Go | All versions | 1.14.7 |
How do I fix CVE-2026-82399?
Upgrade github.com/coredns/coredns to 1.14.7 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-82399 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-82399 exists.
Sources
Also known as AZL-101838, CLEANSTART-2026-MG32349, ECHO-45c5-eafd-f64c, GHSA-mrg3-qvqr-jw29, GO-2026-6507, MINI-25xq-m3x2-4xpv and 19 more.