CVE-2026-74598

Status: UPDATED  |  Advisory ID: CVE-2026-74598

Key Details

Affected Products, Subsystems & Sectors

What to Know

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. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References