{"cve":"CVE-2021-46955","nvd":{"published":"2024-02-27T19:04:06.667","modified":"2026-08-04T10:16:37.990","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nopenvswitch: fix stack OOB read while fragmenting IPv4 packets\n\nrunning openvswitch on kernels built with KASAN, it's possible to see the\nfollowing splat while testing fragmentation of IPv4 packets:\n\n BUG: KASAN: stack-out-of-bounds in ip_do_fragment+0x1b03/0x1f60\n Read of size 1 at addr ffff888112fc713c by task handler2/1367\n\n CPU: 0 PID: 1367 Comm: handler2 Not tainted 5.12.0-rc6+ #418\n Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014\n Call Trace:\n  dump_stack+0x92/0xc1\n  print_address_description.constprop.7+0x1a/0x150\n  kasan_report.cold.13+0x7f/0x111\n  ip_do_fragment+0x1b03/0x1f60\n  ovs_fragment+0x5bf/0x840 [openvswitch]\n  do_execute_actions+0x1bd5/0x2400 [openvswitch]\n  ovs_execute_actions+0xc8/0x3d0 [openvswitch]\n  ovs_packet_cmd_execute+0xa39/0x1150 [openvswitch]\n  genl_family_rcv_msg_doit.isra.15+0x227/0x2d0\n  genl_rcv_msg+0x287/0x490\n  netlink_rcv_skb+0x120/0x380\n  genl_rcv+0x24/0x40\n  netlink_unicast+0x439/0x630\n  netlink_sendmsg+0x719/0xbf0\n  sock_sendmsg+0xe2/0x110\n  ____sys_sendmsg+0x5ba/0x890\n  ___sys_sendmsg+0xe9/0x160\n  __sys_sendmsg+0xd3/0x170\n  do_syscall_64+0x33/0x40\n  entry_SYSCALL_64_after_hwframe+0x44/0xae\n RIP: 0033:0x7f957079db07\n Code: c3 66 90 41 54 41 89 d4 55 48 89 f5 53 89 fb 48 83 ec 10 e8 eb ec ff ff 44 89 e2 48 89 ee 89 df 41 89 c0 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 48 89 44 24 08 e8 24 ed ff ff 48\n RSP: 002b:00007f956ce35a50 EFLAGS: 00000293 ORIG_RAX: 000000000000002e\n RAX: ffffffffffffffda RBX: 0000000000000019 RCX: 00007f957079db07\n RDX: 0000000000000000 RSI: 00007f956ce35ae0 RDI: 0000000000000019\n RBP: 00007f956ce35ae0 R08: 0000000000000000 R09: 00007f9558006730\n R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000\n R13: 00007f956ce37308 R14: 00007f956ce35f80 R15: 00007f956ce35ae0\n\n The buggy address belongs to the page:\n page:00000000af2a1d93 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112fc7\n flags: 0x17ffffc0000000()\n raw: 0017ffffc0000000 0000000000000000 dead000000000122 0000000000000000\n raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000\n page dumped because: kasan: bad access detected\n\n addr ffff888112fc713c is located in stack of task handler2/1367 at offset 180 in frame:\n  ovs_fragment+0x0/0x840 [openvswitch]\n\n this frame has 2 objects:\n  [32, 144) 'ovs_dst'\n  [192, 424) 'ovs_rt'\n\n Memory state around the buggy address:\n  ffff888112fc7000: f3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\n  ffff888112fc7080: 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00 00 00 00\n >ffff888112fc7100: 00 00 00 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00\n                                         ^\n  ffff888112fc7180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\n  ffff888112fc7200: 00 00 00 00 00 00 f2 f2 f2 00 00 00 00 00 00 00\n\nfor IPv4 packets, ovs_fragment() uses a temporary struct dst_entry. Then,\nin the following call graph:\n\n  ip_do_fragment()\n    ip_skb_dst_mtu()\n      ip_dst_mtu_maybe_forward()\n        ip_mtu_locked()\n\nthe pointer to struct dst_entry is used as pointer to struct rtable: this\nturns the access to struct members like rt_mtu_locked into an OOB read in\nthe stack. Fix this changing the temporary variable used for IPv4 packets\nin ovs_fragment(), similarly to what is done for IPv6 few lines below.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","score":7.1},"cwes":["CWE-125"],"references":["https://git.kernel.org/stable/c/23e17ec1a5eb53fe39cc34fa5592686d5acd0dac","https://git.kernel.org/stable/c/490ad0a2390442d0a7b8c00972a83dbb09cab142","https://git.kernel.org/stable/c/5a52fa8ad45b5a593ed416adf326538638454ff1","https://git.kernel.org/stable/c/7c0ea5930c1c211931819d83cfb157bff1539a4c","https://git.kernel.org/stable/c/a1478374b0bda89b4277a8afd39208271faad4be"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:45:59.823092188+00:00"},"epss":{"cve":"CVE-2021-46955","score":0.00746,"percentile":0.54829,"date":"2026-11-01"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}