Location
§11.2, HTTP Message Signature Requirements, line 1143.
Problem
The verifier currently rejects any presentation containing more than one signature tagged human-continuity.
An intermediary or other request-mutating party can append a structurally valid same-tag candidate that does not cryptographically verify, causing rejection of the legitimate signature. RFC 9421 explicitly discusses this multiple-signature injection risk in §7.2.6.
Required resolution
Define bounded candidate processing rather than rejecting solely on multiplicity:
- examine same-tag candidates within documented resource limits;
- accept only a candidate that verifies and satisfies the artifact/holder-key binding;
- allow non-accepted candidates to contribute no verifier output or signature-derived replay inputs; and
- continue recording every otherwise-applicable challenge and profile replay key.
The candidate bound should align with HTTP header-size limits so it does not create a new trivial rejection threshold.
Location
§11.2, HTTP Message Signature Requirements, line 1143.
Problem
The verifier currently rejects any presentation containing more than one signature tagged
human-continuity.An intermediary or other request-mutating party can append a structurally valid same-tag candidate that does not cryptographically verify, causing rejection of the legitimate signature. RFC 9421 explicitly discusses this multiple-signature injection risk in §7.2.6.
Required resolution
Define bounded candidate processing rather than rejecting solely on multiplicity:
The candidate bound should align with HTTP header-size limits so it does not create a new trivial rejection threshold.