CVE Catalog

CVE-2026-72333

Low risk· EPSS 11%
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.21%

11th percentile - higher than 11% of all known CVEs

Summary

A vulnerability in the Linux kernel Bluetooth L2CAP subsystem causes an identifier (ident) leak for commands without a response. Specifically, repeated L2CAP_LE_CREDITS packets exhaust the 1-255 ident range, leading to packets with invalid ident 0 and permanent channel stall for LE CoC.

Risk Assessment

A remote attacker over Bluetooth can cause denial of service by stalling data transmission on an LE CoC channel. After receiving approximately 0.5 MB of data, the channel becomes unusable and credit packets are dropped by the remote stack.

Recommendation

Apply the Linux kernel patch that releases the ident immediately after sending L2CAP_LE_CREDITS and adds the missing L2CAP_LE_CONN_RSP case to l2cap_put_ident(). Update to a kernel version containing this fix.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: fix tx ident leak for commands without a response Commit 6c3ea155e5ee ("Bluetooth: L2CAP: Fix not tracking outstanding TX ident") changed ident allocation to use an IDA, releasing idents in l2cap_put_ident() when the matching response command is received. But identifiers allocated for commands that have no response defined are never released. In particular L2CAP_LE_CREDITS is sent repeatedly for the lifetime of an LE CoC channel, so a peer streaming data to the host exhausts the 1-255 ident range after 254 credit packets. From then on l2cap_get_ident() fails: kernel: Bluetooth: Unable to allocate ident: -28 and every subsequent L2CAP_LE_CREDITS packet is sent with ident 0, which is invalid (Core Spec, Vol 3, Part A, Section 4: "Signaling identifier 0x00 is an invalid identifier and shall never be used in any command"). Remote stacks that validate the ident drop these commands, never receive new credits, and the channel stalls permanently. With default socket buffers this happens after roughly 0.5 MB of received data (the exact amount depends on the socket receive buffer): < ACL Data TX: Handle 2048 flags 0x00 dlen 12 LE L2CAP: LE Flow Control Credit (0x16) ident 0 len 4 Source CID: 64 Credits: 1 Release the ident immediately after sending L2CAP_LE_CREDITS since no response will ever release it. Use a local variable instead of chan->ident so that an ident that an EXT_FLOWCTL channel may be waiting on (e.g. a pending reconfigure) is not overwritten by a credit packet. Also add the missing L2CAP_LE_CONN_RSP case to l2cap_put_ident() so idents allocated for outgoing L2CAP_LE_CONN_REQ commands are released when the response arrives.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS