CVE-2026-74598 ipv6: fix Route Information option length validation
A flaw in Linux kernel IPv6 Route Information option validation allows attackers to read out-of-bounds memory, potentially exposing sensitive data from network packets.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74598?
CVE-2026-74598 is a high-severity vulnerability in Linux, published on 22 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-74598?
How do I fix CVE-2026-74598?
Apply the vendor's patch.
Is CVE-2026-74598 being exploited?
There is no known exploitation of CVE-2026-74598 in the wild and no public exploit code.
Sources
Also known as AZL-97214, BELL-CVE-2026-74598, DEBIAN-CVE-2026-74598, GHSA-vf8p-r5fr-wx72, UBUNTU-CVE-2026-74598.