[CP] Fix path migration UAF: guard path promotion with InUse check (#6217) - #6220
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Summary Fixes a use-after-free in QUIC path migration where a stale/removed path could be promoted into Paths[0] during post-processing. Root Cause When QuicConnReplaceRetiredCids is called during NEW_CONNECTION_ID frame processing, it may invoke QuicPathRemove, which frees the path. However, QuicConnRecvPostProcessing later attempts to promote that same path (via the *Path pointer) if it has non-probing frames and a new largest packet number — without verifying the path is still valid. Fix Add a (*Path)->InUse check in QuicConnRecvPostProcessing before promoting a path to active. This ensures we never promote a path that has already been removed by QuicPathRemove.
Anthony Rossi (anrossi)
approved these changes
Aug 11, 2026
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## release/2.4 #6220 +/- ##
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- Coverage 87.22% 85.78% -1.45%
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Files 56 56
Lines 17348 17348
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- Hits 15132 14882 -250
- Misses 2216 2466 +250 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Guillaume Hetier (guhetier)
merged commit Aug 11, 2026
583e7d5
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release/2.4
375 of 378 checks passed
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Description
Fixes a use-after-free in QUIC path migration where a stale/removed path could be promoted into Paths[0] during post-processing.
Root Cause
When QuicConnReplaceRetiredCids is called during NEW_CONNECTION_ID frame processing, it may invoke QuicPathRemove, which frees the path. However, QuicConnRecvPostProcessing later attempts to promote that same path (via the *Path pointer) if it has non-probing frames and a new largest packet number — without verifying the path is still valid.
Fix
Add a (*Path)->InUse check in QuicConnRecvPostProcessing before promoting a path to active. This ensures we never promote a path that has already been removed by QuicPathRemove.
Testing
CI and validation on a repro of the issue
Documentation
N/A