{"id":"CVE-2026-32934","aliases":["GHSA-2wpx-qpw2-g5h5","GO-2026-4969"],"title":"CoreDNS' DoQ worker pool does not bound stream backlog","summary":"CoreDNS' DoQ worker pool does not bound stream backlog","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","vendor":"coredns","product":"github.com/coredns/coredns","ecosystem":"go","affected":["github.com/coredns/coredns < 1.14.3"],"patched":["github.com/coredns/coredns 1.14.3"],"published":"2026-04-28","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:51:00.935219451Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-2wpx-qpw2-g5h5","references":[{"url":"https://github.com/coredns/coredns/security/advisories/GHSA-2wpx-qpw2-g5h5"},{"url":"https://github.com/coredns/coredns/security/advisories/GHSA-cvx7-x8pj-x2gw"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-32934"},{"url":"https://github.com/coredns/coredns"},{"url":"https://github.com/coredns/coredns/releases/tag/v1.14.3"}],"tags":["osv","go"],"epss":0.00469,"epssPercentile":0.39741,"ingestedAt":"2026-09-12T03:13:01.746Z","slug":"CVE-2026-32934","body":"## Overview\n\n### 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.\n\n## Affected packages\n\n- `github.com/coredns/coredns < 1.14.3`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `github.com/coredns/coredns 1.14.3`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}