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CVE-2026-98541— fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： fou：在 FOU_ENCAP_DIRECT 模式下拒绝缺失的 FOU_ATTR_IPPROTO 属性 提交 7a9bc9e3f423（"fou：不允许 FOU_ATTR_IPPROTO 为 0"）在 中添加了 ，该策略会拒绝显式提供的值为 0 的 属性，并返回 错误。 然而， 是一个可选的 Netlink 属性。当用户发送 命令，将 设置为 但完全省略 属性时， 验证会通过，且 函数会将 保留为 0（该值来自 的初始化）。随后， 会创建一个 的 套接字。 在 函数中，

AI Predicted 7.8 Difficulty: Easy

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63< fd20220f86947d66d4dba2d76f13a28dbd86ef30 affected
23461551c00628c3f3fe9cf837bf53cf8f212b63< 46b1ffb7e169c7e401dd890b29e55dbc261f8f01 affected
23461551c00628c3f3fe9cf837bf53cf8f212b63< 7f4ba56f5d310dd018972916167985010a5d66a1 affected
23461551c00628c3f3fe9cf837bf53cf8f212b63< 3bcc1624cc1cdcc05b566475d6e848093ab2a8f6 affected
23461551c00628c3f3fe9cf837bf53cf8f212b63< 8b43f40798bb2758489fbbcae7e841ad4443c213 affected
23461551c00628c3f3fe9cf837bf53cf8f212b63< b1229b210ef5a39c58be665e6798203751411842 affected
23461551c00628c3f3fe9cf837bf53cf8f212b63< 520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221 affected
23461551c00628c3f3fe9cf837bf53cf8f212b63< d22609f3d13fc5baacd92c222731b03c593401db affected
… +10 more rows
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I. Basic Information for CVE-2026-98541

Vulnerability Information
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Vulnerability Title
fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT Commit 7a9bc9e3f423 ("fou: Don't allow 0 for FOU_ATTR_IPPROTO.") added NLA_POLICY_MIN(NLA_U8, 1) to fou_nl_policy[FOU_ATTR_IPPROTO], which rejects an explicitly supplied FOU_ATTR_IPPROTO == 0 attribute with -ERANGE. However, FOU_ATTR_IPPROTO is an optional netlink attribute. When a user sends FOU_CMD_ADD with FOU_ATTR_TYPE set to FOU_ENCAP_DIRECT and omits FOU_ATTR_IPPROTO entirely, nla_policy validation succeeds and parse_nl_config() leaves cfg->protocol as 0 (from memset(cfg, 0, sizeof(*cfg))). fou_create() then creates a FOU_ENCAP_DIRECT socket with fou->protocol == 0. In fou_udp_recv(), returning -fou->protocol to udp_queue_rcv_one_skb() triggers IP protocol resubmission when fou->protocol > 0, whereas returning 0 tells the UDP tunnel layer that the skb was consumed without freeing it. When fou->protocol == 0, every packet received on the socket returns 0 from fou_udp_recv() and leaks the sk_buff. Reject FOU_ENCAP_DIRECT when !cfg->protocol in fou_create() so that creating a direct encapsulation port without FOU_ATTR_IPPROTO fails with -EINVAL while leaving FOU_CMD_DEL and FOU_CMD_GET (which share parse_nl_config()) unaffected. Tested in QEMU against Linux 7.3.0-rc3 by sending a FOU_CMD_ADD Generic Netlink request with FOU_ATTR_PORT = 5555 and FOU_ATTR_TYPE = FOU_ENCAP_DIRECT while omitting FOU_ATTR_IPPROTO. On the unfixed kernel, FOU_CMD_ADD succeeds (err = 0), FOU_CMD_GET reports fou->type = 1 and fou->protocol = 0, and sending 4000 UDP packets to 127.0.0.1:5555 leaks all 4000 sk_buffs (SUnreclaim in /proc/meminfo grows from 41456 kB to 59008 kB, +17552 kB); with this patch applied, FOU_CMD_ADD is rejected with -EINVAL (-22).
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63 ~ fd20220f86947d66d4dba2d76f13a28dbd86ef30 -
Linux Linux 3.18 -

II. Public POCs for CVE-2026-98541

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III. Intelligence Information for CVE-2026-98541

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Patches & Fixes for CVE-2026-98541 (8)

Same Patch Batch · Linux · 2026-10-18 · 436 CVEs total

CVE-2026-98583 nfc: nfcmrvl: validate helper command length before pull
CVE-2026-98570 net: ipv6: keep room for the mac header in dst_dev_overhead()
CVE-2026-98571 net: stmmac: clear stale buf->page after recycling on skb build failure
CVE-2026-98572 bpf: Fix immediate JMP JEQ/JNE on MIPS32
CVE-2026-98573 net: skbuff: fix pull-bound underflow in skb_checksum_setup_ipv6()
CVE-2026-98574 net: bcmgenet: stop Tx NAPI before disabling the queues
CVE-2026-98575 nfc: pn533: fix OOB read in pn533_acr122_is_rx_frame_valid()
CVE-2026-98576 nfc: llcp: fix slab-out-of-bounds reads when logging service names
CVE-2026-98577 nfc: llcp: fix WKS SAP hijacking via prefix match in nfc_llcp_wks_sap()
CVE-2026-98578 nfc: st21nfca: validate ISO15693 inventory length
CVE-2026-98579 nfc: llcp: fix sdreq TLV list leak on parse/alloc/send failure
CVE-2026-98580 nfc: llcp: Fix race condition in accept_queue lifecycle
CVE-2026-98581 nfc: llcp: Fix list corruption / refcount desync in nfc_llcp_recv_dm()
CVE-2026-98582 nfc: st21nfca: validate received frame size
CVE-2026-98594 tg3: clean up PHYLIB resources on probe failure
CVE-2026-98591 bpf: Fix bounds check for skb-backed dynptrs
CVE-2026-98592 net: spacemit: clear TX descriptor on fragment mapping failure
CVE-2026-98593 s390/debug: Fix NULL pointer dereference in debug_info_copy()
CVE-2026-98590 bpf: Fix bpf_sock context code generation
CVE-2026-98595 udp: remove a disconnected socket from the 4-tuple hash table

Showing top 20 of 436 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-98541

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