High severity · published Oct 8, 2026
CVE-2026-97031
Reject malformed ECH outer extension references in crypto/tls
7.5
CVSS
0.5%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 44% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CR
crypto/tls · Go standard library
before 1.26.9; 1.27.0-0 before 1.27.2 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-97031
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-97031
go.dev
https://go.dev/cl/847312
go.dev
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
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