fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT
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 succee
CVE-2026-98541
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-98541
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"lessThan": "fd20220f86947d66d4dba2d76f13a28dbd86ef30",
"versionType": "git"
},
{
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"lessThan": "46b1ffb7e169c7e401dd890b29e55dbc261f8f01",
"versionType": "git"
},
{
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"lessThan": "7f4ba56f5d310dd018972916167985010a5d66a1",
"versionType": "git"
},
{
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"lessThan": "3bcc1624cc1cdcc05b566475d6e848093ab2a8f6",
"versionType": "git"
},
{
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"lessThan": "8b43f40798bb2758489fbbcae7e841ad4443c213",
"versionType": "git"
},
{
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"lessThan": "b1229b210ef5a39c58be665e6798203751411842",
"versionType": "git"
},
{
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"lessThan": "520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221",
"versionType": "git"
},
{
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"lessThan": "d22609f3d13fc5baacd92c222731b03c593401db",
"versionType": "git"
}
],
"programFiles": [
"net/ipv4/fou_core.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "3.18"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "3.18",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.271",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.222",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.189",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.158",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.112",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.55",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.9",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/ipv4/fou_core.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-98541
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #38568 · Revision 1
- Added to Heist Feed
- Publisher date