VulnerabilityPublished 9 Jul 2026

CVE-2026-53602: nebula-mesh · Host revocation is not durable - blocked/offboarded hosts can regain a valid certificate

Affects github.com/forgekeep/nebula-meshSource GCVE Database

Authoritative record:CVE-2026-53602· Medium 6.9

Not known to be exploited · CVSS 6.9 Medium : upgrade to 0.3.7 when convenient.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 4.0 base score

6.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.3.7

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade github.com/forgekeep/nebula-mesh to 0.3.7.

Affected software

Product	Affected	Fixed in
Gogithub.com/forgekeep/nebula-mesh	Affected <0.3.7	Fixed in 0.3.7

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

## Summary Two related authorization gaps let a host that should no longer be trusted obtain a fresh, valid Nebula certificate, because nebula-mgmt does not re-evaluate revocation/authorization state at certificate *issuance* time — only at poll time. ## 1. Blocklist not enforced at sign / re-enroll time `internal/api/enroll.go:128` calls `caMgr.Sign(...)` without consulting the blocklist. The blocklist is only checked in the poll path (`internal/api/updates.go:57`, `fingerprintInBlocklist`). The blocklist is keyed by certificate *fingerprint* (`internal/store/sqlite.go`), so a re-enrollment produces a new fingerprint that is not in the blocklist. `mintEnrollmentTokenForHost` (`internal/api/hosts.go:491`) authorizes the caller via `canAccessHost` but does **not** check the host status. There is no guard preventing a `blocked` host from transitioning back to `enrolled` (`internal/store/sqlite.go`, `enrollHostInTx` updates status unconditionally). **Impact:** A host that an operator has blocked can be silently un-blocked by issuing a new enrollment token and re-enrolling — it receives a fresh certificate (new fingerprint) that passes all subsequent poll-time blocklist checks. Revocation is therefore not durable. Requires an operator action (minting a re-enroll token), so this is an integrity/operational-revocation failure rather than an unauthenticated bypass. ## 2. Renewal does not re-validate operator / CA status Auto-renewal at poll time (`internal/api/updates.go:285-319`, `signHostCert`) reads `host.Name`, `host.Groups`, `host.NebulaIPs` from the DB and re-signs without checking whether the owning operator is still active or the CA still valid. `DisableOperator` (`internal/store/sqlite_operators.go`) revokes sessions and API keys but does not retire the operator's CAs, and `pki/signer.go` checks only CA cert time-expiry, not operator/CA status. **Impact:** A host enrolled under an operator who is later disabled continues to renew its certificate indefinitely. Offboarding an operator does not cut off the hosts they provisioned. ## Affected versions Latest tagged release (v0.3.6) and `main`. ## Remediation 1. Call a blocklist/status guard inside `handleEnroll` and `signHostCert` **before** `caMgr.Sign(...)`; refuse issuance for a host whose status is `blocked` or whose previous fingerprint is on the blocklist. Require an explicit unblock before re-enroll. 2. At renewal, re-resolve the owning operator/CA status and reject renewal if the operator is disabled or the CA retired (force re-enrollment instead). ## Discovery Found during an internal source + offensive security audit (tracking issue #178). Adversarially cross-verified against the code paths above.

CWE-613Insufficient Session Expiration (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
According to WASC, "Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization."
Implementation
Set sessions/credentials expiration date.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V2.8.1 (opens in a new tab)
V2.8.6 (opens in a new tab)
V3.6.1 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-862Missing Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #4OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
Attack patterns
Exploitation of Thunderbolt Protection Flaws (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-613, CWE-862

Technical details

References

Community reviews

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