EUVD-2026-87523
GHSA-2rm8-9g74-xwqp
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessReach Browser Relay endpoint over network
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DeliveryOpen many WebSocket upgrade connections
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ExploitHold slots without completing Auth v2
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ExecutionExhaust pending-authentication capacity
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ImpactPaired extensions blocked from pairing
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V2 - Validation and Business Logic Resource consumption limits
MITRE ATT&CK
1 technique across 1 tactic: Impact The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Requires network access to the OpenClaw Browser extension relay endpoint that accepts WebSocket upgrades for Browser Relay Authentication v2; no authentication, credentials, or user interaction are needed (PR:N/UI:N). Exploitation succeeds against default configurations wherever the Browser Relay is exposed and reachable. Limiting factors: impact is availability-only and confined to blocking new/paired extension authentication (VA:L) - it does not crash the Gateway, corrupt data, or disclose information, and the condition clears once held connections are released or the pending-auth window expires; deployments that do not expose the Browser Relay to untrusted networks are not reachable. |
| Impact | All signals point to a genuine but low-priority availability issue. The vendor CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L) is internally consistent with the description: an unauthenticated, network-reachable, low-complexity resource-exhaustion flaw whose ONLY impact is low-level availability loss (VA:L) - no confidentiality or integrity exposure. The 6.9 base score is driven almost entirely by the unauthenticated network reachability, not by impact severity; the actual damage is confined to blocking new Browser extension pairings, not crashing the Gateway or exposing data. There is no EPSS score, no CISA KEV listing, and no public POC identified at time of analysis, so there is no evidence of active or imminent exploitation. Signals are mutually consistent (no CVSS-vs-description conflict), so confidence in the 'network unauthenticated DoS, availability-only' characterization is high. Net: real and remotely triggerable, but a narrow, self-resolving denial of a single subsystem - patch on normal cadence rather than emergency. |
| Exploit ScenarioDerived | An unauthenticated attacker with network reach to the OpenClaw Browser Relay endpoint opens many WebSocket upgrade connections and holds them silently without completing Browser Relay Authentication v2, consuming every pending-authentication slot. With all slots held, legitimate paired browser extensions can no longer complete authentication and are locked out until the connections drop or the window clears. No public exploit code is identified, and the attack requires no credentials or user interaction. |
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Alert meAnalysisAIv1 – Sep 26, 2026
Denial of service in OpenClaw's Browser extension relay allows unauthenticated network attackers to exhaust the pool of pending-authentication slots by holding silent WebSocket upgrade connections open, which blocks legitimately paired browser extensions from completing Browser Relay Authentication v2. All OpenClaw builds before 2026.8.2 are affected per the vendor advisory and CPE cpe:2.3:a:openclaw:openclaw, with no public exploit identified at time of analysis and no confirmed actively exploited (CISA KEV) status. Impact is availability-only and limited to authentication slot exhaustion - scored 6.9 under CVSS 4.0 (AV:N/AC:L/AT:N/PR:N/UI:N/VA:L) and assessed independently as CVSS 3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - meaning the Gateway itself is not crashed, data is neither corrupted nor disclosed, and service resumes once held connections are released or the pending-auth window expires.
RemediationAI
Upgrade OpenClaw to 2026.8.2 or later - the vendor-released fix for this issue - following the guidance in GHSA-m78m-7h3q-q938 (https://github.com/openclaw/openclaw/security/advisories/GHSA-m78m-7h3q-q938) and the VulnCheck advisory (https://www.vulncheck.com/advisories/openclaw-before-2026.8.2-denial-of-service-via-browser-relay); no other vendor-released patch version is documented in the available data. Where immediate upgrade is not possible, the most effective compensating control is network scoping: bind the Browser extension relay to loopback or a management VLAN and firewall the relay's WebSocket port so only known extension hosts can reach it, accepting that this breaks remote or roaming extension pairing until the upgrade is applied. Secondary controls include placing an authenticating reverse proxy in front of the relay and rate-limiting or capping concurrent WebSocket upgrade attempts per source while shortening the pending-authentication timeout, which reduces the ease of slot exhaustion but adds latency to legitimate pairing and may cause occasional pairing failures when slots are briefly saturated; note that these measures mitigate the symptom and do not remove the underlying unbounded-slot-occupancy flaw, since the defect is availability-only and self-clears once held connections are released.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
The flaw is a CWE-400 uncontrolled resource consumption condition in OpenClaw's Browser extension relay, the component that brokers WebSocket connections between the OpenClaw Gateway and paired browser extensions. Browser Relay Authentication v2 maintains a bounded set of pending-authentication slots for in-progress WebSocket upgrade handshakes; an attacker with network reachability to the relay endpoint can open upgrades and keep them silent (never completing the handshake or authenticating), occupying every slot until the pending-auth window times out. Because the pending-slot pool is a finite per-connection resource rather than a per-identity quota, occupancy by unauthenticated peers denies the same slots to legitimate extensions, producing a functional lockout of the relay rather than a crash or memory-corruption condition. The CVSS 4.0 vector carries PR:N/UI:N, so no credentials and no user action are required; reachability of the relay from an untrusted network segment is the sole gate. The accompanying EUVD record (EUVD-2026-87523) and CPE string scope every OpenClaw release from 0 up to but excluding 2026.8.2.
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Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Unauthenticated network attacker with low complexity and no user interaction (AV:N/AC:L/PR:N/UI:N); impact is limited, self-resolving availability loss of one subsystem, so A:L and C:N/I:N.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
1DescriptionCVE.org
OpenClaw before 2026.8.2 contains a denial of service vulnerability in the Browser extension relay that allows unauthenticated network sources to exhaust pending-authentication capacity. Attackers can hold every pending slot by maintaining silent WebSocket upgrades, preventing paired extensions from completing Browser Relay Authentication v2.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
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