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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
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needs backport to 3.14
gpshead
marked this pull request as ready for review
November 1, 2026 18:13
gpshead
enabled auto-merge (squash)
November 1, 2026 18:14
gpshead
added
needs backport to 3.11
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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