{ "schema_version": "1.6.1", "id": "RPI-CVE-2024-41007", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2024-41007" ], "published": "2024-07-15T08:48:21Z", "summary": "tcp: avoid too many retransmit packets", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: avoid too many retransmit packets\n\nIf a TCP socket is using TCP_USER_TIMEOUT, and the other peer\nretracted its window to zero, tcp_retransmit_timer() can\nretransmit a packet every two jiffies (2 ms for HZ=1000),\nfor about 4 minutes after TCP_USER_TIMEOUT has 'expired'.\n\nThe fix is to make sure tcp_rtx_probe0_timed_out() takes\nicsk->icsk_user_timeout into account.\n\nBefore blamed commit, the socket would not timeout after\nicsk->icsk_user_timeout, but would use standard exponential\nbackoff for the retransmits.\n\nAlso worth noting that before commit e89688e3e978 (\"net: tcp:\nfix unexcepted socket die when snd_wnd is 0\"), the issue\nwould last 2 minutes instead of 4.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.21-1+rpt1", "1:6.1.47-1+rpt2", "1:6.1.47-1+rpt4", "1:6.1.54-1+rpt2", "1:6.1.58-1+rpt2", "1:6.1.63-1+rpt1", "1:6.1.73-1+rpt1", "1:6.6.20-1+rpt1", "1:6.6.28-1+rpt1", "1:6.6.31-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi1-rpi-v6", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi1-rpi-v7", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi1-rpi-v7l", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi1-rpi-v8", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi2-rpi-v6", "binary_version": "1:6.1.47-1+rpt2" }, { "binary_name": "linux-image-6.1.0-rpi2-rpi-v7", "binary_version": "1:6.1.47-1+rpt2" }, { "binary_name": 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"https://git.kernel.org/stable/c/d2346fca5bed130dc712f276ac63450201d52969" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/5d7e64d70a11d988553a08239c810a658e841982" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/04317a2471c2f637b4c49cbd0e9c0d04a519f570" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/e113cddefa27bbf5a79f72387b8fbd432a61a466" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/dfcdd7f89e401d2c6616be90c76c2fac3fa98fde" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/66cb64a1d2239cd0309f9b5038b05462570a5be1" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/97a9063518f198ec0adb2ecb89789de342bb8283" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T11:52:36Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.5, "cvss_v3_severity": "High", "scenario": "AV:N - The bug is in the core TCP stack (net/ipv4/tcp_timer.c) and is driven entirely by a remote peer's advertised window and ACKs; no local access is needed. Any remote TCP peer of a socket with TCP_USER_TIMEOUT set (NFS client transports, ocfs2, BPF-sockops-configured connections, gRPC/Envoy/HAProxy/Redis servers) can trigger it.\nAC:L - The attacker fully controls the trigger \u2014 shrink the receive window to zero (stop reading, or use a custom stack) and keep ACKing the zero-window probes to keep tp->rcv_tstamp fresh so tcp_rtx_probe0_timed_out() never aborts. No race, timing luck, or memory-layout dependency; TCP_USER_TIMEOUT being set is a common attacker-independent deployment property (sunrpc sets it unconditionally), i.e. part of the vulnerable configuration.\nPR:N - No authentication or credentials are required \u2014 establishing a TCP connection and getting unacked data in flight (e.g. a banner or a pre-auth response) is sufficient. Locally the same condition is reachable by any unprivileged user via setsockopt(TCP_USER_TIMEOUT), which has no capability check.\nUI:N - The packet storm is generated autonomously by the kernel retransmit timer once the peer advertises a zero window. No action by any local user or administrator is needed.\nS:U - The CPU, softirq and network-bandwidth exhaustion stay within the affected host's own security authority. No privilege or virtualization boundary is crossed.\nC:N - The bug only causes excessive retransmission of data already queued for and destined to that same peer \u2014 no out-of-bounds read, uninitialized memory, or kernel-pointer exposure. The only extra output is an already-existing net_dbg_ratelimited() message.\nI:N - There is no memory corruption, out-of-bounds write, or type confusion; the emitted packets are legitimate, correctly-formed retransmissions. No kernel or user data is modified.\nA:H - tcp_clamp_rto_to_user_timeout() pins the retransmit timer to 1 jiffy, producing 500\u20131000 packets/sec per socket, each with a tcp_enter_loss() and a __sk_dst_reset() route lookup, and a peer that keeps ACKing probes makes this unbounded in time rather than the 4 minutes noted in the changelog. Scaled across many connections this is a sustained, unauthenticated CPU and link-saturation denial of service, and the socket also silently ignores the TCP_USER_TIMEOUT the application relies on for failure detection." } } }