{"id":"CVE-2026-32934","aliases":["GHSA-2wpx-qpw2-g5h5","GO-2026-4969"],"url":"https://o3.security/vulnerability/CVE-2026-32934","summary":"CoreDNS DNS-over-QUIC unbounded goroutine growth leads to denial of service","details":"### Summary\nCoreDNS' DNS-over-QUIC (DoQ) server can be driven into large goroutine and memory growth by a remote client that opens many QUIC streams and stalls after sending only 1 byte. Even with a small configured quic { worker_pool_size ... }, CoreDNS still spawns a goroutine per accepted stream (workers + waiters) and active workers can block indefinitely in io.ReadFull() with no per-stream read deadline, enabling unauthenticated remote DoS via memory exhaustion/OOM-kill.\n\n### Details\nCoreDNS' DoQ server uses a global worker pool (streamProcessPool) to limit concurrent stream processing, but when the pool is full it still spawns a goroutine per accepted stream that waits to acquire a worker token: select { case s.streamProcessPool <- ...: go ...; default: go ... wait for token ... } (core/dnsserver/server_quic.go)\n\nAdditionally, the DoQ message framing reads are blocking io.ReadFull() calls with no per-stream read deadline: readDOQMessage() reads the 2-byte length prefix and message body via io.ReadFull() (core/dnsserver/server_quic.go)\n\nThis allows an attacker to pin all workers by sending 1 byte (so io.ReadFull() blocks waiting for the second byte of the DoQ length prefix), while also creating an unbounded backlog of goroutines waiting for a worker token.\n\nNote: this appears to be a result of an incomplete fix/regression for CVE-2025-47950 (GHSA-cvx7-x8pj-x2gw).\n\n### PoC\n1. Adjust COREDNS_BIN in the PoC to point at right path (see the top-level const definitions for tunables as well)\n2. Run python3 ./doq-dos-repro.py\n3. Expected sample output:\n*** Start CoreDNS ***\nCorefile: /tmp/vh-f003-doq-mem-regression/Corefile\nLog: /tmp/vh-f003-doq-mem-regression/coredns.log\n\n*** Baseline sample (idle) ***\nrss_kib=49380 go_goroutines=17\n\n*** Build + run partial-stream flooder ***\ngo: downloading golang.org/x/net v0.43.0\ngo: downloading golang.org/x/crypto v0.41.0\ngo: downloading go.uber.org/mock v0.5.2\ngo: downloading github.com/stretchr/testify v1.11.1\ngo: downloading golang.org/x/sys v0.35.0\ngo: downloading github.com/pmezard/go-difflib v1.0.0\ngo: downloading github.com/davecgh/go-spew v1.1.1\ngo: downloading gopkg.in/yaml.v3 v3.0.1\n\n*** Candidate sample (during attack) ***\nrss_kib=137968 go_goroutines=15557\n\n*** Flooder output ***\nopened conns=60 streams_per_conn=256 total_streams=15360\n\n*** Wrote results ***\n/tmp/vh-f003-doq-mem-regression/results.json\n\n*** OK ***\nDoQ flood caused goroutine/RSS growth despite worker_pool_size.\n\n\n### Impact\nUnauthenticated remote DoS on an encrypted DNS transport via goroutine/RSS growth leading to OOM-kill/crash and service outage.","published":"2026-05-05T19:06:17.080Z","modified":"2026-08-12T03:51:27.959479417Z","cvss":null,"epss":{"score":0.00469,"percentile":0.39303,"asOf":"2026-09-15"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/coredns/coredns","fixedVersion":"1.14.3"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/coredns/coredns/releases/tag/v1.14.3"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/32xxx/CVE-2026-32934.json"},{"type":"ADVISORY","url":"https://github.com/coredns/coredns/security/advisories/GHSA-2wpx-qpw2-g5h5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-32934"},{"type":"WEB","url":"https://github.com/coredns/coredns/security/advisories/GHSA-cvx7-x8pj-x2gw"},{"type":"PACKAGE","url":"https://github.com/coredns/coredns"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:27.959479417Z"}}