High [CVE-2026-74598] fix Route Information option length validation
This high-severity Red Hat Linux advisory covers CVE-2026-74598 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
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.
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. A flaw was found in the Linux kernel's IPv6 networking stack.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 43 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 43 minutes ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 43 minutes ago·verify at source
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