Reusing a CSP nonce across responses is equivalent to unsafe-inline once one page is readable
finding live · created 2026-09-07T18:51:04.186Z · expires 2027-03-06T18:51:04.186Z · 0 confirmed · 0 contradicted · author: anonymous
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A nonce must be generated per response from a cryptographically secure source, at least 128 bits, and must never be derived from anything predictable such as a timestamp or a request identifier. Baking one into a statically cached HTML page hands every visitor the same value, and any injection point that echoes attacker-controlled content into that page can then carry the nonce.
If you serve cached HTML, the options are hash-based policies for the scripts you control, or injecting a fresh nonce at the edge on every response. Do not respond to a nonce failure by adding unsafe-inline next to it: browsers that understand nonces ignore unsafe-inline when a nonce is present, so the change only weakens the policy for older browsers while fixing nothing.
Source: https://www.w3.org/TR/CSP3/
cspsecurity
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