# CVE-2026-73500: etcd TLS listener denial of service via connection exhaustion

Source: https://junglewise.ai/threats/cve-2026-73500-etcd-tls-listener-denial-of-service-via-connection-exhaustion  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-12. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-73500 · Severity: medium · CVSS 4 · Published 2026-08-12

etcd is a distributed key-value store that manages configuration and state for systems like Kubernetes clusters. A network attacker can establish many TCP connections to the TLS listener without completing the handshake, causing the process to consume unbounded memory and crash. When etcd backs a Kubernetes control plane, this leads to complete cluster unavailability.

Technologies: [go.etcd.io/etcd/v3 (Go)](https://junglewise.ai/threats/technologies/go-etcd-io-etcd-v3). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-73500 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-73500 being exploited in the wild.

**How severe is CVE-2026-73500?** Medium severity, with a CVSS score of 4, published 12 August 2026.

**Which products and versions are affected?** go.etcd.io/etcd/client/pkg/v3 (Go) SEMVER:introduced=0,fixed=3.5.33,introduced=3.6.0,fixed=3.6.14,introduced=3.7.0-alpha.0,fixed=3.7.1; go.etcd.io/etcd/v3 (Go) SEMVER:introduced=3.7.0-alpha.0,fixed=3.7.1.

**Is there a fix for CVE-2026-73500?** Yes. go.etcd.io/etcd/client/pkg/v3 (Go): upgrade to 3.7.1 or later; go.etcd.io/etcd/v3 (Go): upgrade to 3.7.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-73500 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-73500?** Check whether you run go.etcd.io/etcd/client/pkg/v3 (Go) or go.etcd.io/etcd/v3 (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- go.etcd.io/etcd/client/pkg/v3 (Go): upgrade to 3.7.1 or later

  ```sh
  go get go.etcd.io/etcd/client/pkg/v3@v3.7.1
  ```

- go.etcd.io/etcd/v3 (Go): upgrade to 3.7.1 or later

  ```sh
  go get go.etcd.io/etcd/v3@v3.7.1
  ```


## Technical details

The vulnerability is a denial-of-service flaw in the TLS connection handling code (client/pkg/transport/listener_tls.go). When a client connects to the TLS listener but never sends a ClientHello message, the acceptLoop spawns a goroutine that blocks indefinitely in tls.Conn.Handshake() while remaining tracked in a pending connection map. An attacker on the network can open many such incomplete connections, causing unbounded growth of goroutines and the pending map, exhausting memory and crashing the etcd process. The fix implements a tlsHandshakeTimeout to bound the duration of incomplete handshakes. Versions 3.5.33, 3.6.14, and 3.7.1 and later are patched.

## Affected products

- etcd etcd prior to 3.5.33, 3.6.14, and 3.7.1

## Identifiers

- CVE-2026-73500
- GHSA-6vch-q96h-7gc3
- GO-2026-6107

## Timeline

- 2026-08-12: disclosed
- 2026-08-12: patched: Versions 3.5.33, 3.6.14, and 3.7.1 and later

## References

- [https://github.com/etcd-io/etcd/commit/2e07efce9745004eb4773cffaada9b5cdf77cff2](https://github.com/etcd-io/etcd/commit/2e07efce9745004eb4773cffaada9b5cdf77cff2)
- [https://github.com/etcd-io/etcd/commit/89ff6d50796049d4f1136915ba21504b76e7e372](https://github.com/etcd-io/etcd/commit/89ff6d50796049d4f1136915ba21504b76e7e372)

## Related threats

- [etcd authorization bypass in Watch gRPC API](https://junglewise.ai/threats/cve-2026-73499-etcd-authorization-bypass-in-watch-grpc-api)
- [etcd RBAC authorization bypass in transaction operations](https://junglewise.ai/threats/cve-2026-44283-etcd-rbac-authorization-bypass-in-transaction-operations)
- [GO-2026-4808 - Nested etcd transactions bypass RBAC authorization checks in go.etcd.io/etcd](https://junglewise.ai/threats/cve-2026-33343-etcd-nested-etcd-transactions-bypass-rbac-authorization-checks)
- [GO-2026-4806 - Authorization bypasses in multiple APIs in go.etcd.io/etcd](https://junglewise.ai/threats/cve-2026-33413-etcd-authorization-bypasses-in-multiple-apis)
- [GO-2024-2528 - Etcd Gateway TLS endpoint validation only confirms TCP reachability in go.etcd.io/etcd](https://junglewise.ai/threats/go-2024-2528-etcd-gateway-tls-endpoint-validation-only-confirms-tcp-0788e9d2)