Nobody reads the label
IETF says servers must be identified. Seven widely-used stacks don’t enforce — four comply. Nobody owns the name and no examiner checks the claim, so a stack can wear “TLS 1.3” while skipping the very check that stops a server being impersonated.
20 May 2026
A label on a tin of food has an inspector behind it. So does the safety mark on a plug, and the star rating on a car: a lab, a body, someone who can withhold the mark. The label that matters most to the traffic crossing the internet has no inspector at all. “TLS 1.3” is applied by the people who wrote the code, to their own work. No lab tests it. No certificate hangs on a wall.
That is no scandal. It is how nearly all protocols ship, and the honour system has carried the internet a long way. But it does mean the label is a claim — and a claim is only as good as the part nobody checked.
Here is a small, sharp, entirely checkable part: every certificate carries a label, written by the authority that issued it, saying what the key inside can do. For servers, that label says can sign; one marked the other way must never sign. None of this is a judgement call: one signed, machine-readable bit. The only question left is whether the code looks.
Seven do not. Hand seven widely-used libraries a real certificate — from a trusted authority, with a matching name, marked by that authority as forbidden to sign — and they ignore the forbidden instruction. What it costs is impersonation. A certificate its authority marked unusable for signing is used to sign, the handshake completes, and whoever holds that certificate is accepted as the site it names.
The certificate carries a label its reader ignores. The library carries a label nobody checks. Only one of those is a bug.
Four do. Give the identical certificate to four other libraries and they read the label and stop. Four independent teams, in four languages, with no coordination between them, reached the same verdict. The strict reading is not exotic, not a matter of taste, and not something invented for the occasion — it is shipping, in production, in four places, today. Whatever else can be said about the other seven, “it was ambiguous” cannot.
“TLS 1.3” is a defined thing, and to ship it is to promise all of it. So the honest options are: deliver on promises, or drop the claim. The honour system only works if the label is true. Read on →