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crypto/tls: reject malformed ECH outer extension references #81855
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.
This is CVE-2026-97031 and Go issue https://go.dev/issue/81855.
This was a PRIVATE track issue originally tracked in http://b/539665253.
Activity
thatnealpatel commentedon Sep 30, 2026
@gopherbot Please open backports for this security issue.
gopherbot commentedon Sep 30, 2026
Backport issue(s) opened: #81915 (for 1.26), #81916 (for 1.27).
Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.
gopherbot commentedon Oct 8, 2026
Change https://go.dev/cl/847025 mentions this issue:
[release-branch.go1.27] crypto/tls: validate ECH outer extension referencesgopherbot commentedon Oct 8, 2026
Change https://go.dev/cl/847105 mentions this issue:
[release-branch.go1.26] crypto/tls: validate ECH outer extension references[release-branch.go1.27] crypto/tls: validate ECH outer extension refe…
[release-branch.go1.26] crypto/tls: validate ECH outer extension refe…
gopherbot commentedon Oct 8, 2026
Change https://go.dev/cl/847312 mentions this issue:
crypto/tls: validate ECH outer extension references[-]security: fix CVE-2026-97031[/-][+]crypto/tls: reject malformed ECH outer extension references[/+]crypto/tls: validate ECH outer extension references
crypto/tls: validate ECH outer extension references