{"id":"CVE-2026-99139","title":"tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)\n\ndo_tcp_getsockopt() reads icsk->icsk_ca_ops->name without holding\nrcu_read_lock(). Since commit 0baf26b0fc…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2 < c1804ef016392dd91267d2207ee43b1de34302ca","Linux >= 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2 < a8e45471afa230c1431c26c8e99ec24377e3b514","Linux >= 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2 < 5271b79b7ad68dcb222e893773f92bdabf7750f3","Linux 5.6"],"published":"2026-10-28","updated":"2026-10-28","sourceUpdated":"2026-10-28T10:34:50.674Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99139","references":[{"url":"https://git.kernel.org/stable/c/c1804ef016392dd91267d2207ee43b1de34302ca"},{"url":"https://git.kernel.org/stable/c/a8e45471afa230c1431c26c8e99ec24377e3b514"},{"url":"https://git.kernel.org/stable/c/5271b79b7ad68dcb222e893773f92bdabf7750f3"}],"tags":["cve.org"],"ingestedAt":"2026-10-28T11:09:40.429Z","slug":"CVE-2026-99139","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ntcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)\n\ndo_tcp_getsockopt() reads icsk->icsk_ca_ops->name without holding\nrcu_read_lock(). Since commit 0baf26b0fcd7 (\"bpf: tcp: Support\ntcp_congestion_ops in bpf\"), icsk_ca_ops can point to dynamically\nallocated BPF struct_ops memory that may be freed concurrently via\nsetsockopt(TCP_CONGESTION), leading to a use-after-free.\n\n  BUG: KASAN: slab-use-after-free in _copy_to_user+0x37/0x60\n  Read of size 16 at addr ffff888013505260 by task exploit/149\n   _copy_to_user+0x37/0x60\n   do_tcp_getsockopt+0x158a/0x2460 (net/ipv4/tcp.c:4585)\n   tcp_getsockopt+0x91/0xf0\n   __sys_getsockopt+0xf7/0x170\n\nFix this by holding rcu_read_lock() around the ca_ops->name access,\nusing READ_ONCE() to load icsk_ca_ops, and copying the name to a\nstack buffer before releasing the lock. Also annotate the relevant\nicsk_ca_ops stores with WRITE_ONCE() to fix the accompanying KCSAN\ndata-race issue.\n\n## Affected\n\n- `Linux >= 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2 < c1804ef016392dd91267d2207ee43b1de34302ca`\n- `Linux >= 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2 < a8e45471afa230c1431c26c8e99ec24377e3b514`\n- `Linux >= 0baf26b0fcd74bbfcef53c5d5e8bad2b99c8d0d2 < 5271b79b7ad68dcb222e893773f92bdabf7750f3`\n- `Linux 5.6`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}