fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98541
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-18 16:17:05 UTC
Updated2026-10-18 16:17:05 UTC
DescriptionIn 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).

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 fd20220f86947d66d4dba2d76f13a28dbd86ef30 git Not specified
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 46b1ffb7e169c7e401dd890b29e55dbc261f8f01 git Not specified
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 7f4ba56f5d310dd018972916167985010a5d66a1 git Not specified
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 3bcc1624cc1cdcc05b566475d6e848093ab2a8f6 git Not specified
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 8b43f40798bb2758489fbbcae7e841ad4443c213 git Not specified
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 b1229b210ef5a39c58be665e6798203751411842 git Not specified
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221 git Not specified
CNA Linux Linux affected 23461551c00628c3f3fe9cf837bf53cf8f212b63 d22609f3d13fc5baacd92c222731b03c593401db git Not specified
CNA Linux Linux affected 3.18 Not specified
CNA Linux Linux unaffected 3.18 semver Not specified
CNA Linux Linux unaffected 5.10.271 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.222 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.189 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.158 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.112 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.55 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.9 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/3bcc1624cc1cdcc05b566475d6e848093ab2a8f6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7f4ba56f5d310dd018972916167985010a5d66a1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/46b1ffb7e169c7e401dd890b29e55dbc261f8f01 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d22609f3d13fc5baacd92c222731b03c593401db 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fd20220f86947d66d4dba2d76f13a28dbd86ef30 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8b43f40798bb2758489fbbcae7e841ad4443c213 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b1229b210ef5a39c58be665e6798203751411842 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report