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CVE-2026-46306

flow_dissector: do not dissect PPPoE PFC frames

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 6.1.175, 6.6.140, 6.12.88, 6.18.30, 7.0.7
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: partial

Summary

In the Linux kernel, the following vulnerability has been resolved: flow_dissector: do not dissect PPPoE PFC frames RFC 2516 Section 7 states that Protocol Field Compression (PFC) is NOT RECOMMENDED for PPPoE. In practice, pppd does not support negotiating PFC for PPPoE sessions, and the flow dissector driver has assumed an uncompressed frame until the blamed commit. During the review process of that commit [1], support for PFC is suggested. However, having a compressed (1-byte) protocol field means the subsequent PPP payload is shifted by one byte, causing 4-byte misalignment for the network header and an unaligned access exception on some architectures. The exception can be reproduced by sending a PPPoE PFC frame to an ethernet interface of a MIPS board, with RPS enabled, even if no PPPoE session is active on that interface: $ 0 : 00000000 80c40000 00000000 85144817 $ 4 : 00000008 00000100 80a75758 81dc9bb8 $ 8 : 00000010 8087ae2c 0000003d 00000000 $12 : 000000e0 00000039 00000000 00000000 $16 : 85043240 80a75758 81dc9bb8 00006488 $20 : 0000002f 00000007 85144810 80a70000 $24 : 81d1bda0 00000000 $28 : 81dc8000 81dc9aa8 00000000 805ead08 Hi : 00009d51 Lo : 2163358a epc : 805e91f0 __skb_flow_dissect+0x1b0/0x1b50 ra : 805ead08 __skb_get_hash_net+0x74/0x12c Status: 11000403 KERNEL EXL IE Cause : 40800010 (ExcCode 04) BadVA : 85144817 PrId : 0001992f (MIPS 1004Kc) Call Trace: [<805e91f0>] __skb_flow_dissect+0x1b0/0x1b50 [<805ead08>] __skb_get_hash_net+0x74/0x12c [<805ef330>] get_rps_cpu+0x1b8/0x3fc [<805fca70>] netif_receive_skb_list_internal+0x324/0x364 [<805fd120>] napi_complete_done+0x68/0x2a4 [<8058de5c>] mtk_napi_rx+0x228/0xfec [<805fd398>] __napi_poll+0x3c/0x1c4 [<805fd754>] napi_threaded_poll_loop+0x234/0x29c [<805fd848>] napi_threaded_poll+0x8c/0xb0 [<80053544>] kthread+0x104/0x12c [<80002bd8>] ret_from_kernel_thread+0x14/0x1c Code: 02d51821 1060045b 00000000 <8c640000> 3084000f 2c820005 144001a2 00042080 8e220000 To reduce the attack surface and maintain performance, do not process PPPoE PFC frames. [1] https://lore.kernel.org/r/20220630231016.GA392@debian.home

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: partial

  3. Record last updated

Affected versions

  • Linux Linux

    From 10f665b52a75df6eb26ddebbbc072ee264183731 · fixed in e7c811ca372d53c2be7d01a1614e71fae1054836; From d7e541e86122d21f71eb71c5dfa7fb1eb6623fe8 · fixed in abc5bc84e0f2edc7ea2d437afa6ef3fe1fc43200; From 46126db9c86110e5fc1e369b9bb89735ddefdae4 · fixed in 18ae9eacfc95cc715c0606b2c86e8aa8a86cf3e3; From 46126db9c86110e5fc1e369b9bb89735ddefdae4 · fixed in db104b0d8a7856397c0469d83a4289adf7c54863; From 46126db9c86110e5fc1e369b9bb89735ddefdae4 · fixed in 6044392d9cace3a3672b02c8bc7d38b502e51734; From 46126db9c86110e5fc1e369b9bb89735ddefdae4 · fixed in 0d00b9015069712944934bab09eaa6c542143049; From 46126db9c86110e5fc1e369b9bb89735ddefdae4 · fixed in 7c93f353eab4ea911e394630f07d72e040a729d8; From 46126db9c86110e5fc1e369b9bb89735ddefdae4 · fixed in d6c19b31a3c1d519fabdcf0aa239e6b6109b9473

  • Linux Linux

    6.0

  • KernelLinux

    From 6.0.0 · fixed in 6.1.175; From 6.2.0 · fixed in 6.6.140; From 6.7.0 · fixed in 6.12.88; From 6.13.0 · fixed in 6.18.30; From 6.19.0 · fixed in 7.0.7

References 8

git.kernel.org