Bluetooth: L2CAP: fix out-of-bounds write in l2cap_ecred_connect

Summary

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: fix out-of-bounds write in l2cap_ecred_connect l2cap_chan_connect() tries to ensure there are no more than L2CAP_ECRED_CONN_SCID_MAX pending ECRED channels, so they fit in the same L2CAP_ECRED_CONN_REQ that l2cap_ecred_connect() constructs. However, the check only counts deferred channels. If 6 L2CAP sockets are connected at the same time in order DDDDND (D=deferred, N=non-deferred), the last can bump the total to max+1. It results to one __le16 written out of bounds of the scid array, and an invalid ECRED_CONN_REQ being sent. Fix by leaving room for the non-deferred pending ECRED channels in the counting in l2cap_chan_connect(), so the limit can't be exceeded. Move counting under same critical section where the channel is added. Although race conditions involving this appear unreachable, it's easier to see. Also add WARN_ON_ONCE check in l2cap_ecred_defer_connect() to make this less brittle.

Timeline

1. Sep 25, 2026, 10:35 AM UTCCVE published
2. Oct 21, 2026, 12:54 PM UTCRecord last updated

Affected versions

• Linux Linux

  From da49b602f7f75ccc91386e1274b3ef71676cd092 · fixed in fabc5e04f123225daf980d03f2c5a05e7f0f0a7f; From da49b602f7f75ccc91386e1274b3ef71676cd092 · fixed in ce0927eb3ee2939fab5ce3f9334bfd2fafb38481; From da49b602f7f75ccc91386e1274b3ef71676cd092 · fixed in 6da5c0331fc3ef0c7b8df8269523fc3b2cce1e65; From da49b602f7f75ccc91386e1274b3ef71676cd092 · fixed in df8c3af6132640da4788e96a02d653e642059803; From da49b602f7f75ccc91386e1274b3ef71676cd092 · fixed in 56c2b5831d39dc84aad2573dc3e197af1a872a05

• Linux Linux

  5.7

• KernelLinux

  From 5.7.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.111; From 6.13.0 · fixed in 6.18.53; From 6.19.0 · fixed in 7.2.7

References 5