# CVE-2026-97031 — Go standard library crypto/tls

> As of 2026-10-09, CVE-2026-97031 is a HIGH-severity vulnerability in Go standard library crypto/tls, CVSS v3.1 7.5, EPSS 0.1% (6.8th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-97031 as of 2026-10-09; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-10-09

## What is CVE-2026-97031?

Multiple ECH outer extension references are not permitted under RFC 9849; previously, a client could send a well-crafted packet that could trigger memory exhaustion in the server process by specifying multiple references. We now reject these as malformed and curb the memory amplification vector as a result.

The record classifies CVE-2026-97031 under weakness class [CWE-405](https://intel.threadlinqs.com/cwe/CWE-405). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 2 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.5 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 6.8% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-10-08, last modified 2026-10-09

## Is CVE-2026-97031 being exploited?

It currently carries a trending score of 31 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [Go standard library](https://intel.threadlinqs.com/vendors/go-standard-library): crypto/tls

## How to fix CVE-2026-97031

No vendor patch reference has been recorded for CVE-2026-97031 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-97031

No threat campaign in the Threadlinqs corpus currently references CVE-2026-97031, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, GitHub Security Advisories, FIRST EPSS. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [go.dev](https://go.dev/cl/847312)
- [go.dev (81855)](https://go.dev/issue/81855)
- [groups.google.com](https://groups.google.com/g/golang-announce/c/U2fTuyDJznI)
- [pkg.go.dev](https://pkg.go.dev/vuln/GO-2026-6607)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-97031
Full detection coverage and IOCs for threats exploiting CVE-2026-97031 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp