# CVE-2026-119776: frr: ospf6d fails to enforce all OSPFv3 packets use IPv6 link-local addresses

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

In all prior released versions of FRRouting, the OSPFv3 (for IPv6) implementation does not check that OSPFv3 packets have a link-local source address and either a link-local destination or one of the protocol multicast destination groups.  This may enable malicious actors to establish OSPFv3 adjacencies from unexpectedly, distant IPv6 hosts. Proper usage of OSPFv3 authentication trailers (RFC 7166, as is best practice) prevents full exploitation of this issue, though may allow a malicious actor to waste CPU on authentication checks.


Note the linked PR #23935 is not sufficient to fix the issue as it only verifies the source address. It is the destination address that must be checked.


Required configuration: The OSPFv3 for IPv6 routing protocol must be running (ospf6d process) and in use (enabled globally with "router ospf6" and on specific interfaces with "ipv6 ospf6 area".)


Workaround: either:

  *  configure OSPFv3 authentication trailers ("ipv6 ospf6 authentication")
  *  or ensure through firewall configuration that only packets with link-local or multicast destination addresses are accepted on input for IPv6 protocol 89 (OSPF). Note that checking the source address is insufficient, as some routers may (unexpectedly) forward packets with global-scoped IPv6 destination addresses even if they have link-local source addresses.

## Remediation

- workaround: Either:

  *  configure OSPFv3 authentication trailers ("ipv6 ospf6 authentication")
  *  or ensure through firewall configuration that only packets with link-local or multicast destination addresses are accepted on input for IPv6 protocol 89 (OSPF). Note that checking the source address is insufficient, as some routers may (unexpectedly) forward packets with global-scoped IPv6 destination addresses even if they have link-local source addresses. (source: CNA: NetDEF)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: NetDEF) — https://github.com/FRRouting/frr/pull/24183/changes/eaccfcdb35bce8d94621b06633417ba3fa657f34

## Affected products and versions

- frrouting / frrouting: ≥ 0; < * (affected, git); unaffected at eaccfcdb35bce8d94621b06633417ba3fa657f34. Source: CNA: NetDEF

## Severity and prioritization

- CVSS 4.0: 6.1 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:H/VA:H/SC:N/SI:N/SA:N/AU:Y; source: CNA: NetDEF

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-304

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/FRRouting/frr/pull/24183/changes/eaccfcdb35bce8d94621b06633417ba3fa657f34 (CNA: NetDEF; patch)

- https://github.com/FRRouting/frr/pull/24183 (CNA: NetDEF; related)

- https://github.com/FRRouting/frr/pull/23935 (CNA: NetDEF; related)

## Provenance

- CNA: NetDEF: https://www.cve.org/CVERecord?id=CVE-2026-119776; retrieved 2026-11-04; source updated 2026-11-04

Revision: 6aacb3cdbf2601c2fd8d5b941889d207732c4014a7ba985c565b7f6ecc2779b8

Canonical: https://y2.dev/cve/CVE-2026-119776

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