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Vulnerabilities

Vulnerability · CVE-2026-97031

Reject malformed ECH outer extension references in crypto/tls

Published Oct 8, 2026 · catalog updated Oct 16, 2026 · Reject malformed ECH outer

Check if you run it

No confirmed exploitation is on record for CVE-2026-97031. EPSS is 0.39%. Act only if a listed version of Reject malformed ECH outer is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Reject malformed ECH outer).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Unknown—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.39%
Remediation
Not established
Affected products
Go stdlib

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Go stdlib0 → 1.26.9

How to fix CVE-2026-97031

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-97031. EPSS is 0.39%. Act only if a listed version of Reject malformed ECH outer is installed.

Which versions are affected?

Compare what you have installed with 0 → 1.26.9. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.39%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 8, 2026 · Go Vulnerability Database

    Detected

    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.

  2. Oct 16, 2026 · Go Vulnerability Database

    Fix available

    stdlib fixed in 1.26.9

  3. Oct 16, 2026 · Go Vulnerability Database

    Fix available

    stdlib fixed in 1.26.9

  4. Oct 16, 2026 · Go Vulnerability Database

    Updated

    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.

Sources

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.