What’s Vulnerable › Vulnerabilities

CVE-2026-73500: etcd: `tlsListener.acceptLoop` spawns unbounded handshake goroutines with no deadline

• Severity: high (CVSS 8.7 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-12 · updated 2026-10-24
• Weakness: CWE-770

Description

etcd is a distributed key-value store for the data of a distributed system. Prior to versions 3.5.33, 3.6.14, and 3.7.1, a network attacker who can reach an etcd TLS listener can open many TCP connections and never send a ClientHello. In client/pkg/transport/listener_tls.go, each connection handled by tlsListener.acceptLoop spawns a goroutine that blocks indefinitely inside tls.Conn.Handshake() and remains tracked in the pending map. Unbounded goroutine and map growth can exhaust memory in the etcd process, causing loss of availability for the cluster and, when etcd backs Kubernetes, the control plane. This issue is fixed in versions 3.5.33, 3.6.14, and 3.7.1.

Affected products

• etcd-io etcd: before 3.5.33; from 3.6.0, < 3.6.14; from 3.7.0-alpha.0, < 3.7.1

References

• https://github.com/etcd-io/etcd/commit/2e07efce9745004eb4773cffaada9b5cdf77cff2
• https://github.com/etcd-io/etcd/commit/89ff6d50796049d4f1136915ba21504b76e7e372
• https://github.com/etcd-io/etcd/commit/8e4dd0679a2c6b095d2a32a749fda2521c7809a3
• https://github.com/etcd-io/etcd/commit/f73cba7d920019f91a1ea1f6697833e42731f057
• https://github.com/etcd-io/etcd/pull/22130
• https://github.com/etcd-io/etcd/releases/tag/v3.5.33
• https://github.com/etcd-io/etcd/releases/tag/v3.6.14
• https://github.com/etcd-io/etcd/releases/tag/v3.7.1
• https://github.com/etcd-io/etcd/security/advisories/GHSA-6vch-q96h-7gc3

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