[BUG] Fixed OOB read in ACK payload parsing#3325
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ethouris
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Jun 8, 2026
| LOGC(inlog.Warn, log << CONID() << "ACK: payload " << pktlen | ||
| << " bytes is shorter than LITE (" << SEND_LITE_ACK << ") - rejecting"); | ||
| return; | ||
| } |
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If all earlier checks are already there, then for every command packet it's checked if it contains at least a payload of 4 bytes (commands that don't use arguments have at least the 4-byte padding). So this part should be checked anyway before even calling this function. If so, this one is redundant.
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The mentioned changes is in #3323 - so when this one is merged, the check for "LITE" ACK correct size is not necessary.
ethouris
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CUDT::processCtrlAck
reads twoint32_t` fields out of the control packetpayload without validating its length:
ackdata[ACKD_RCVLASTACK](index 0) is dereferenced up front, OOB for0–3 byte payloads.
ackdata[ACKD_BUFFERLEFT](index 3) is dereferenced on the non-lite path,OOB for 5–15 byte payloads.
A peer can send an ACK control packet with an arbitrary intermediate
payload length and cause the receiver to read up to 15 bytes past the
allocated packet buffer. The value at index 3 is then assigned into
m_iFlowWindowSize, so the leaked memory directly perturbs send-sideflow control.
REPLACED BY: #3323