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IDNA normalization maps U+00A0 and similar characters to an ASCII space, so check the encoded host that is put into the CONNECT request line.
gpshead
marked this pull request as ready for review
November 1, 2026 18:13
gpshead
enabled auto-merge (squash)
November 1, 2026 18:14
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I marked this for full backporting security style as it might be a way that #146211 could be bypassed. FYI @SethMichaelLarson ie: if so we should move the news entry to Security. |
gpshead
disabled auto-merge
November 1, 2026 18:22
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Encode the tunnel host with IDNA first and run the existing disallowed-character check on the bytes that go into the
CONNECTrequest line. IDNA passes ASCII through unchanged, so every host refused today is still refused with the same message; the only newly refused hosts are those whose encoding contains a space.The
Hostheader built inputrequest()has the same encode-after-check order, but a host like that can't be resolved for a direct connection, so it is left alone here.Fixes #161104
ANT-2026-PIZPMECM
HTTPConnection.set_tunnel()host check runs before IDNA maps U+00A0 to a space #161104