h3-proxy: fix NULL deref when non-:status header arrives before :status - #22449
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h3-proxy: fix NULL deref when non-:status header arrives before :status#22449SilentSobs wants to merge 1 commit into
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icing
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Jul 31, 2026
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This seems theoretical as :status has to be the first header in a response. But for the sake of defensive coding, it seems good to cope with a possible error in the http3 library.
bagder
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cb_h3_proxy_recv_header() only allocates pctx->tunnel.resp when it sees the :status pseudo-header. Any other header field is stored via pctx->tunnel.resp->headers without checking that resp was actually set, so a header arriving before :status (or a response with no :status at all) crashes with a NULL dereference.
Add a check for pctx->tunnel.resp before use, same as the non-proxy cb_h3_recv_header already does for its stream pointer.
Found via a libFuzzer harness driving curl's H3-proxy callbacks directly.