medium CVSS 5.5 EPSS <0.1%

CVE-2023-52778·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: mptcp: deal with large GSO size After the blamed commit below, the TCP sockets (and the MPTCP subflows) can build egress packets larger than 64K. That exceeds the maximum DSS data size, the length being misrepresent on the wire and the stream being corrupted, as later observed on the receiver: WARNING: CPU: 0 PID: 9696 at net/mptcp/protocol.c:705 __mptcp_move_skbs_from_subflow+0x2604/0x26e0 CPU: 0 PID: 9696 Comm: syz-executor.7 Not tainted 6.6.0-rc5-gcd8bdf563d46 #45 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 netlink: 8 bytes leftover after parsing attributes in process `syz-executor.4'. RIP: 0010:__mptcp_move_skbs_from_subflow+0x2604/0x26e0 net/mptcp/protocol.c:705 RSP: 0018:ffffc90000006e80 EFLAGS: 00010246 RAX: ffffffff83e9f674 RBX: ffff88802f45d870 RCX: ffff888102ad0000 netlink: 8 bytes leftover after parsing attributes in process `syz-executor.4'. RDX: 0000000080000303 RSI: 0000000000013908 RDI: 0000000000003908 RBP: ffffc90000007110 R08: ffffffff83e9e078 R09: 1ffff1100e548c8a R10: dffffc0000000000 R11: ffffed100e548c8b R12: 0000000000013908 R13: dffffc0000000000 R14: 0000000000003908 R15: 000000000031cf29 FS: 00007f239c47e700(0000) GS:ffff88811b200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f239c45cd78 CR3: 000000006a66c006 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 PKRU: 55555554 Call Trace: <IRQ> mptcp_data_ready+0x263/0xac0 net/mptcp/protocol.c:819 subflow_data_ready+0x268/0x6d0 net/mptcp/subflow.c:1409 tcp_data_queue+0x21a1/0x7a60 net/ipv4/tcp_input.c:5151 tcp_rcv_established+0x950/0x1d90 net/ipv4/tcp_input.c:6098 tcp_v6_do_rcv+0x554/0x12f0 net/ipv6/tcp_ipv6.c:1483 tcp_v6_rcv+0x2e26/0x3810 net/ipv6/tcp_ipv6.c:1749 ip6_protocol_deliver_rcu+0xd6b/0x1ae0 net/ipv6/ip6_input.c:438 ip6_input+0x1c5/0x470 net/ipv6/ip6_input.c:483 ipv6_rcv+0xef/0x2c0 include/linux/netfilter.h:304 __netif_receive_skb+0x1ea/0x6a0 net/core/dev.c:5532 process_backlog+0x353/0x660 net/core/dev.c:5974 __napi_poll+0xc6/0x5a0 net/core/dev.c:6536 net_rx_action+0x6a0/0xfd0 net/core/dev.c:6603 __do_softirq+0x184/0x524 kernel/softirq.c:553 do_softirq+0xdd/0x130 kernel/softirq.c:454 Address the issue explicitly bounding the maximum GSO size to what MPTCP actually allows.

Severity
medium
Software
Kernel
Fixed in
6.6.3
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 5% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Affected versions

From: 6.6

Until: 6.6.3

Fixed in: 6.6.3

How to fix this CVE

Update your Linux kernel to version 6.6.3 or later to fix a critical data path issue in MPTCP that causes packet corruption when Generic Segmentation Offload (GSO) exceeds protocol limits. This vulnerability impacts multipath TCP connections and can lead to stream data corruption. Apply the kernel update immediately on all affected systems running kernel versions 6.6.0 through 6.6.2.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check current kernel version: uname -r (vulnerable if output shows 6.6.0, 6.6.1, or 6.6.2)
  2. Verify MPTCP is enabled: grep -i mptcp /boot/config-$(uname -r) (look for CONFIG_MPTCP=y)
  3. Search kernel logs for MPTCP corruption warnings: sudo journalctl -b | grep -i 'mptcp\|__mptcp_move_skbs_from_subflow'
  4. Verify patch applied: grep -i 'GSO size' /proc/version or check commit hash in git log with: git log --oneline | grep -i 'GSO\|mptcp'

FAQ

What is CVE-2023-52778?

CVE-2023-52778 is a kernel vulnerability affecting MPTCP (Multipath TCP) where packets larger than 64KB generated by Generic Segmentation Offload violate the MPTCP Data Sequence Signal (DSS) length limits, causing data corruption on the receiving end.

Is CVE-2023-52778 being actively exploited?

No, CVE-2023-52778 is not listed on the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. However, it affects data integrity and should still be patched promptly.

What versions of Kernel are affected by CVE-2023-52778?

Linux kernel versions 6.6.0 through 6.6.2 are vulnerable. Kernel 6.6.3 and later include the fix.

How do I check if my server is vulnerable to CVE-2023-52778?

Run: uname -r — if the output shows 6.6.0, 6.6.1, or 6.6.2, your system is vulnerable. Additionally verify MPTCP support with: grep CONFIG_MPTCP /boot/config-$(uname -r)

Does Defensia detect CVE-2023-52778?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Linux kernel is installed on a monitored server, CVE-2023-52778 will appear in your dashboard with remediation steps.

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References

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