GoBGP confederation validation panics on empty AS_PATH attribute

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-49838: 0.41% estimated exploitation activity in the next 30 days; percentile 35.53 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Found through variant analysis based on CVE-2026-41643 Summary GoBGP accepts a zero-length ASPATH during UPDATE decoding and later panics while validating that attribute for a confederation eBGP peer. The vulnerable path is in the BGP UPDATE validator: a malformed UPDATE that should be rejected as a malformed ASPATH instead reaches an unchecked p.Value[0] access, allowing a configured confederation eBGP peer to trigger a denial of service. Affected - Project: gobgp - Repo: https://github.com/osrg/gobgp - Pinned ref: c24629411ba49f160d9dc09126f418218127e016 Root cause An established peer's receive path reads BGP bytes from the network connection in pkg/server/fsm.go:1267, parses UPDATE bodies through the BGP message decoder, and validates decoded UPDATEs with peer state at pkg/server/fsm.go:1849. The UPDATE decoder walks the path-attribute list in pkg/packet/bgp/bgp.go:15773 and selects the concrete attribute parser from the attacker-controlled attribute type at…

Published by the source

9 Jul 2026, 23:21 UTC

Last modified by the source

9 Jul 2026, 23:21 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-frrj-87jh-2772

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-49838

Advisory: GoBGP confederation validation panics on empty AS_PATH attribute
IDs: CVE-2026-49838, GHSA-frrj-87jh-2772
Record: https://patchnext.com/advisories/cve-2026-49838 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/osrg/gobgp/v4 4.7.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/osrg/gobgp/v4: affected <= 4.6.0; fixed in 4.7.0

## Suggested inspection (read-only)
- Go github.com/osrg/gobgp/v4: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/osrg/gobgp/v4.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-frrj-87jh-2772 (GitHub-reviewed advisory GHSA-frrj-87jh-2772 lists affected ranges: Go github.com/osrg/gobgp/v4 >=0 <=4.6.0)

Commands are suggestions: review each one before running it.