net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop
In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6_nh_init() misclassifies it as a reject route. This is because nexthop objects have no destination prefix (fc_dst=::), causing fib6_is_reject() to match any loopback nexthop. The reject path skips fib_nh_common_init(), leaving nhc_pcpu_rth_output unallocated. If an IPv4 route later references this nexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and panics. Simplify the check in fib6_nh_init() to only match explicit reject routes (RTF_REJECT) instead of using fib6_is_reject(). The loopback promotion heuristic in fib6_is_reject() is handled separately by ip6_route_info_create_nh(). After this change, the three cases behave as follows: 1. Explicit reject route ("ip -6 route add unreachable 2001:db8::/64"): RTF_REJECT is set, enters reject path, skips fib_nh_common_init(). No behavior change. 2. Implicit loopback reject route ("ip -6 route add 2001:db8::/32 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. ip6_route_info_create_nh() still promotes it to reject afterward. nhc_pcpu_rth_output is allocated but unused, which is harmless. 3. Standalone nexthop object ("ip -6 nexthop add id 100 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. nhc_p
CVE-2026-23300
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-2026-23300
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": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
"lessThan": "607e68c1b7c5a30c795571be1906d716e989a644",
"versionType": "git"
},
{
"status": "affected",
"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
"lessThan": "c11d7c56c2076ee9cd72004f1976fe0734df2ae9",
"versionType": "git"
},
{
"status": "affected",
"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
"lessThan": "b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a",
"versionType": "git"
},
{
"status": "affected",
"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
"lessThan": "b299121e7453d23faddf464087dff513a495b4fc",
"versionType": "git"
},
{
"status": "affected",
"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
"lessThan": "f7c9f8e3607440fe39300efbaf46cf7b5eecb23f",
"versionType": "git"
},
{
"status": "affected",
"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
"lessThan": "b3b5a037d520afe3d5276e653bc0ff516bbda34c",
"versionType": "git"
},
{
"status": "affected",
"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
"lessThan": "8650db85b4259d2885d2a80fbc2317ce24194133",
"versionType": "git"
},
{
"status": "affected",
"version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
"lessThan": "21ec92774d1536f71bdc90b0e3d052eff99cf093",
"versionType": "git"
}
],
"programFiles": [
"net/ipv6/route.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.3"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.3",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.253",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.203",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.167",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.130",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.77",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.17",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "6.19.7",
"versionType": "semver",
"lessThanOrEqual": "6.19.*"
},
{
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/ipv6/route.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-23300
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #27218 · Revision 1
- Added to Heist Feed
- Publisher date