EUVD-2026-64535
GHSA-vf8p-r5fr-wx72
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Router Advertisements are link-local by RFC 4861 protocol design, making AV:A correct; no authentication or user interaction required; confidentiality impact only.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
ipv6: fix Route Information option length validation
rt6_route_rcv() validates the Route Information option (RFC 4191) length against the prefix length, but both checks are off by one.
rinfo->length is the ND option length in units of 8 octets and it *includes* the 8-byte option header, so an option carrying N bytes of prefix has length == 1 + N/8. RFC 4191 section 2.3 requires length 3 when Prefix Length is greater than 64, and 2 or 3 when it is greater than 0. The code accepts length >= 2 and length >= 1 respectively.
ipv6_addr_prefix() then copies prefix_len/8 bytes out of rinfo->prefix, so a Router Advertisement with (prefix_len=128, length=2) or (prefix_len=64, length=1) makes the kernel read up to 8 bytes past the end of the option. Those bytes end up in the prefix of the route that gets installed, so they are visible to userspace:
RA with a Route Information option (prefix_len=128, length=2)
followed by a source link-layer address option, 01 01 de ad be ef ca fe
$ ip -6 route show 2001:db8:dead:beef:101:dead:beef:cafe via fe80::1234 dev veth0 proto ra ^^^^^^^^^^^^^^^^^^ the next option, read out of bounds
When the Route Information option is the last one in the packet, those eight bytes come from the skb tail room instead.
Reject the option lengths RFC 4191 does not allow.
AnalysisAI
Out-of-bounds memory read in the Linux kernel's IPv6 stack exposes up to 8 bytes of adjacent kernel memory per crafted Router Advertisement. The flaw in rt6_route_rcv() permits a link-local attacker to send a Route Information option with an RFC 4191-invalid prefix_len/length combination, causing ipv6_addr_prefix() to read beyond the option boundary and install the overread bytes as a route prefix visible to unprivileged userspace via ip -6 route show. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to be on the same IPv6 link as the target system (link-local adjacency), since Router Advertisements are constrained by protocol to hop limit 255 and cannot traverse routers. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The NVD-assigned CVSS 3.1 score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) overstates the attack distance: Router Advertisements are link-scoped by protocol (IPv6 hop limit 255, link-local source addresses per RFC 4861), making AV:A a more accurate characterization with a resulting score near 6.5. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with access to the same IPv6 network link as a target Linux host - or controlling an upstream router - crafts a raw Router Advertisement containing a Route Information option with prefix_len=128 and the RFC 4191-invalid length=2, then broadcasts it to the link-local all-nodes multicast address (ff02::1). The kernel's `rt6_route_rcv()` passes the malformed option through the relaxed length check, and `ipv6_addr_prefix()` reads 8 bytes past the option boundary; if another ND option immediately follows, those bytes (e.g., a source link-layer address option `01 01 de ad be ef ca fe`) are incorporated into the installed route prefix and visible to any local user running `ip -6 route show`. … |
| Remediation | The primary fix is upgrading to a patched stable kernel release: 5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104, 6.18.45, 7.1.9, or 7.2. … Detailed patch versions, workarounds, and compensating controls in full report. |
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