Vulnerability-Lookup

CVE-2026-61699 (GCVE-0-2026-61699)

Vulnerability from cvelistv5 – Published: 2026-09-04 19:43 – Updated: 2026-09-08 12:59

Title

nebula-mesh: Certificate revocation is never enforced at the mesh

Summary

nebula-mesh is a self-hosted control plane for Slack Nebula mesh VPN. Prior to version 0.7.1, revocation is the only in-band mechanism that isolates a compromised/offboarded host from a Nebula mesh. Because the blocklist never reaches any peer's config.yml, a Blocked host retains full overlay reachability to every peer under its CA (and internal services on the mesh) for up to 30d (agent) / 365d (mobile). An attacker who exfiltrates host.key+host.crt can run stock slackhq/nebula directly, ignore the agent's 403/410 poll responses, and stay connected after the operator revokes the host. Operator-visible state (UI shows blocked, audit log records it) is misleading. This issue has been patched in version 0.7.1.

Severity

8.1 (High)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-08 12:58 UTC

CWE

CWE-299 - Improper Check for Certificate Revocation
CWE-672 - Operation on a Resource after Expiration or Release

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/forgekeep/nebula-mesh/security…	x_refsource_CONFIRM
https://github.com/forgekeep/nebula-mesh/commit/0…	x_refsource_MISC
https://github.com/forgekeep/nebula-mesh/releases…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
forgekeep	nebula-mesh	Affected: < 0.7.1	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-61699

Vulnerability from fkie_nvd - Published: 2026-09-04 20:17 - Updated: 2026-09-08 21:05

Severity

8.1 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/forgekeep/nebula-mesh/commit/0426e2f224a9b1e2029029bf923c93ed39d21cdb
	security-advisories@github.com	https://github.com/forgekeep/nebula-mesh/releases/tag/v0.7.1
	security-advisories@github.com	https://github.com/forgekeep/nebula-mesh/security/advisories/GHSA-cm26-5974-52h8
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/forgekeep/nebula-mesh/security/advisories/GHSA-cm26-5974-52h8

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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          "product": "nebula-mesh",
          "vendor": "forgekeep",
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}

GHSA-CM26-5974-52H8

Vulnerability from github – Published: 2026-07-14 20:28 – Updated: 2026-07-14 20:28

Summary

nebula-mesh: Certificate revocation is never enforced at the mesh

Details

Summary

nebula-mesh revokes a host by adding its certificate fingerprint to a per-CA blocklist and shipping that list to every other agent on each poll. Slack's Nebula enforces certificate revocation ONLY through the pki.blocklist list in config.yml (no CRL/OCSP). The project's own code states this: internal/pki/durations.go:15 — "Revocation via the blocklist remains the immediate security control."

The server side is fully implemented (computes per-CA blocklist via GetBlocklistForCA, returns it in the agent-updates response, sets has_updates=true when non-empty). The agent side was never implemented:

The agent decodes the blocklist JSON field into UpdatesResponse.Blocklist (internal/agent/poller.go:33) and then DISCARDS it — poll() applies CertificatePEM, CACertPEM, ConfigYAML, but never references updates.Blocklist (internal/agent/poller.go:300-339).
The config generator has NO field to emit pki.blocklist — pkiSection is only ca/cert/key (internal/configgen/marshal.go:42-46) and GeneratorInput carries no blocklist (internal/configgen/generator.go:23-52). So even the server-rendered config.yml shipped via ConfigYAML cannot carry it.

Result: a blocked/offboarded/compromised host's certificate is never rejected by its peers. Its handshakes keep succeeding for the full remaining cert lifetime — up to 30 days for agent hosts (DefaultAgentCertDuration) and 365 days for mobile hosts (DefaultMobileCertDuration). Blocking a host in the UI/API has no effect on the data plane.

Affected components

Agent drops the blocklist: internal/agent/poller.go:33 (decode target), internal/agent/poller.go:300-339 (poll() applies cert/CA/config, never the blocklist).
Generator cannot emit it: internal/configgen/marshal.go:42-46 (pkiSection{CA,Cert,Key}), internal/configgen/generator.go:23-52 (GeneratorInput has no blocklist), internal/api/enroll.go:255-330 (renderHostConfig, source of shipped ConfigYAML).
Server correctly produces/ships it (proves intent): internal/store/sqlite.go:2034 (GetBlocklistForCA), internal/api/updates.go:182-191 (resp.Blocklist), internal/api/updates.go:277 (has_updates set on blocklist change).
Dead helper: internal/pki/blocklist.go (Blocklist type) is never used in non-test code — no server-side enforcement either.

Reachability (hop by hop)

Operator clicks Block on host B (or B is compromised/offboarded). B's fingerprint enters the per-CA blocklist table.
Every other host A under the same CA polls GET /api/v1/agent/updates; server returns blocklist: [<B-fp>, ...] and has_updates=true.
A's agent decodes Blocklist then discards it; poll() has no blocklist branch.
Even on a config re-render, configgen.Generate emits pki: {ca,cert,key} with no blocklist key (proven by PoC).
A's Nebula daemon has an empty blocklist and accepts handshakes from B's still-valid cert. B keeps full mesh access.

Impact

Revocation is the only in-band mechanism that isolates a compromised/offboarded host from a Nebula mesh. Because the blocklist never reaches any peer's config.yml, a Blocked host retains full overlay reachability to every peer under its CA (and internal services on the mesh) for up to 30d (agent) / 365d (mobile). An attacker who exfiltrates host.key+host.crt can run stock slackhq/nebula directly, ignore the agent's 403/410 poll responses, and stay connected after the operator revokes the host. Operator-visible state (UI shows blocked, audit log records it) is misleading.

Proof of Concept (benign)

internal/configgen/blocklist_poc_test.go renders a fully-populated host config and asserts the output contains the pki section but NO blocklist key:

$ go test ./internal/configgen/ -run TestPoC_NMESH001 -v
=== RUN   TestPoC_NMESH001_GeneratedConfigOmitsBlocklist
    CONFIRMED: generated config has a pki section but no blocklist key
    pki:
      ca: /etc/nebula/ca.crt
      cert: /etc/nebula/host.crt
      key: /etc/nebula/host.key
    ...
--- PASS

The agent half is verifiable by inspection: poll() has branches for CertificatePEM/CACertPEM/ConfigYAML/RekeyRequired but none for Blocklist.

Distinctness

NOT a duplicate of GHSA-339v / CVE-2026-53602 (revocation durability = a blocked host getting a NEW cert re-issued; its fix CheckIssuanceAllowed is present and orthogonal). This bug is that the EXISTING cert is never rejected at peers — the distribution/enforcement layer. Checked against all 17 known advisories; none cover blocklist application in the agent or pki.blocklist generation.

Remediation

Add Blocklist []safeString to pkiSection (yaml blocklist,omitempty) and GeneratorInput; consider also pki.disconnect_invalid: true.
Have the agent apply updates.Blocklist by re-rendering/rewriting config.yml + SIGHUP (same path as ConfigYAML). Simplest: fold the blocklist into the server-rendered ConfigYAML so it flows through the existing write path.
Add a regression test asserting a non-empty server blocklist yields a pki.blocklist entry in the agent's written config.yml.

Severity

8.1 (High)


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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/forgekeep/nebula-mesh"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.7.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-61699"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-299",
      "CWE-672"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-14T20:28:18Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\nnebula-mesh revokes a host by adding its certificate fingerprint to a per-CA blocklist and shipping that list to every other agent on each poll. Slack\u0027s Nebula enforces certificate revocation ONLY through the `pki.blocklist` list in `config.yml` (no CRL/OCSP). The project\u0027s own code states this: `internal/pki/durations.go:15` \u2014 \"Revocation via the blocklist remains the immediate security control.\"\n\nThe server side is fully implemented (computes per-CA blocklist via `GetBlocklistForCA`, returns it in the agent-updates response, sets `has_updates=true` when non-empty). The agent side was never implemented:\n\n1. The agent decodes the `blocklist` JSON field into `UpdatesResponse.Blocklist` (`internal/agent/poller.go:33`) and then DISCARDS it \u2014 `poll()` applies `CertificatePEM`, `CACertPEM`, `ConfigYAML`, but never references `updates.Blocklist` (`internal/agent/poller.go:300-339`).\n2. The config generator has NO field to emit `pki.blocklist` \u2014 `pkiSection` is only `ca`/`cert`/`key` (`internal/configgen/marshal.go:42-46`) and `GeneratorInput` carries no blocklist (`internal/configgen/generator.go:23-52`). So even the server-rendered `config.yml` shipped via `ConfigYAML` cannot carry it.\n\nResult: a blocked/offboarded/compromised host\u0027s certificate is never rejected by its peers. Its handshakes keep succeeding for the full remaining cert lifetime \u2014 up to 30 days for agent hosts (`DefaultAgentCertDuration`) and 365 days for mobile hosts (`DefaultMobileCertDuration`). Blocking a host in the UI/API has no effect on the data plane.\n\n### Affected components\n\n- Agent drops the blocklist: `internal/agent/poller.go:33` (decode target), `internal/agent/poller.go:300-339` (poll() applies cert/CA/config, never the blocklist).\n- Generator cannot emit it: `internal/configgen/marshal.go:42-46` (`pkiSection{CA,Cert,Key}`), `internal/configgen/generator.go:23-52` (`GeneratorInput` has no blocklist), `internal/api/enroll.go:255-330` (`renderHostConfig`, source of shipped ConfigYAML).\n- Server correctly produces/ships it (proves intent): `internal/store/sqlite.go:2034` (`GetBlocklistForCA`), `internal/api/updates.go:182-191` (`resp.Blocklist`), `internal/api/updates.go:277` (`has_updates` set on blocklist change).\n- Dead helper: `internal/pki/blocklist.go` (`Blocklist` type) is never used in non-test code \u2014 no server-side enforcement either.\n\n### Reachability (hop by hop)\n\n1. Operator clicks Block on host B (or B is compromised/offboarded). B\u0027s fingerprint enters the per-CA `blocklist` table.\n2. Every other host A under the same CA polls `GET /api/v1/agent/updates`; server returns `blocklist: [\u003cB-fp\u003e, ...]` and `has_updates=true`.\n3. A\u0027s agent decodes `Blocklist` then discards it; `poll()` has no blocklist branch.\n4. Even on a config re-render, `configgen.Generate` emits `pki: {ca,cert,key}` with no `blocklist` key (proven by PoC).\n5. A\u0027s Nebula daemon has an empty blocklist and accepts handshakes from B\u0027s still-valid cert. B keeps full mesh access.\n\n### Impact\n\nRevocation is the only in-band mechanism that isolates a compromised/offboarded host from a Nebula mesh. Because the blocklist never reaches any peer\u0027s config.yml, a Blocked host retains full overlay reachability to every peer under its CA (and internal services on the mesh) for up to 30d (agent) / 365d (mobile). An attacker who exfiltrates `host.key`+`host.crt` can run stock slackhq/nebula directly, ignore the agent\u0027s 403/410 poll responses, and stay connected after the operator revokes the host. Operator-visible state (UI shows blocked, audit log records it) is misleading.\n\n### Proof of Concept (benign)\n\n`internal/configgen/blocklist_poc_test.go` renders a fully-populated host config and asserts the output contains the `pki` section but NO `blocklist` key:\n\n```\n$ go test ./internal/configgen/ -run TestPoC_NMESH001 -v\n=== RUN   TestPoC_NMESH001_GeneratedConfigOmitsBlocklist\n    CONFIRMED: generated config has a pki section but no blocklist key\n    pki:\n      ca: /etc/nebula/ca.crt\n      cert: /etc/nebula/host.crt\n      key: /etc/nebula/host.key\n    ...\n--- PASS\n```\n\nThe agent half is verifiable by inspection: `poll()` has branches for CertificatePEM/CACertPEM/ConfigYAML/RekeyRequired but none for Blocklist.\n\n### Distinctness\n\nNOT a duplicate of GHSA-339v / CVE-2026-53602 (revocation durability = a blocked host getting a NEW cert re-issued; its fix `CheckIssuanceAllowed` is present and orthogonal). This bug is that the EXISTING cert is never rejected at peers \u2014 the distribution/enforcement layer. Checked against all 17 known advisories; none cover blocklist application in the agent or `pki.blocklist` generation.\n\n### Remediation\n\n1. Add `Blocklist []safeString` to `pkiSection` (yaml `blocklist,omitempty`) and `GeneratorInput`; consider also `pki.disconnect_invalid: true`.\n2. Have the agent apply `updates.Blocklist` by re-rendering/rewriting `config.yml` + SIGHUP (same path as `ConfigYAML`). Simplest: fold the blocklist into the server-rendered `ConfigYAML` so it flows through the existing write path.\n3. Add a regression test asserting a non-empty server blocklist yields a `pki.blocklist` entry in the agent\u0027s written config.yml.",
  "id": "GHSA-cm26-5974-52h8",
  "modified": "2026-07-14T20:28:18Z",
  "published": "2026-07-14T20:28:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/forgekeep/nebula-mesh/security/advisories/GHSA-cm26-5974-52h8"
    },
    {
      "type": "WEB",
      "url": "https://github.com/forgekeep/nebula-mesh/commit/0426e2f224a9b1e2029029bf923c93ed39d21cdb"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/forgekeep/nebula-mesh"
    },
    {
      "type": "WEB",
      "url": "https://github.com/forgekeep/nebula-mesh/releases/tag/v0.7.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "nebula-mesh: Certificate revocation is never enforced at the mesh"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-61699 (GCVE-0-2026-61699)

FKIE_CVE-2026-61699

GHSA-CM26-5974-52H8

Summary

Affected components

Reachability (hop by hop)

Impact

Proof of Concept (benign)

Distinctness

Remediation

Tags

Sightings

Nomenclature

Related by attack behaviour