QTINeon has unauthenticated relay-to-host amplification via unbounded RECONNECT_REQUEST forwarding

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

QTI Neon is a minimal, game-agnostic, relay-based UDP multiplayer protocol library. In version 1.0.0, the relay's handleReconnectRequest forwards RECONNECT_REQUEST packets to the host without bounding them, so an unauthenticated client can drive relay-to-host amplification and cause a denial of service on the host. No fixed version is available as of this review.

Source published

28 Jul 2026 16:36:37 UTC

Source modified

28 Jul 2026 17:07:15 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

QTI Neon is a minimal, game-agnostic, relay-based UDP multiplayer protocol library. In version 1.0.0, the relay's handleReconnectRequest forwards RECONNECT_REQUEST packets to the host without bounding them, so an unauthenticated client can drive relay-to-host amplification and cause a denial of service on the host. No fixed version is available as of this review.

Source published

28 Jul 2026 17:16:52 UTC

Source modified

23 Oct 2026 23:10:00 UTC

Observed here

25 Oct 2026 13:17:28 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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CVSS 3.1 · [email protected] · Secondary · 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

### Impact The relay's reconnect handler forwards every `RECONNECT_REQUEST` to the host without deduplication or a size cap on the `pendingReconnects` map, unlike the connect flow which guards against this with `maxPendingConnections`. An unauthenticated attacker who knows a valid session ID can send `RECONNECT_REQUEST` packets from many spoofed source addresses; each packet that passes the session lookup is forwarded to the host as a new reconnect attempt. Because the per-source rate limiter assigns a fresh token bucket to each spoofed IP, it provides no protection. The host receives one forwarded packet per spoofed source per cleanup cycle, making the relay an amplification vector for denial-of-service against the host. The host's real address is never exposed to clients by design, so this is the primary viable DoS path against it. A secondary issue: once more than `maxRateLimiters` spoofed IPs are seen, `performCleanup` calls `rateLimiters.clear()`, resetting rate limit state for all sources including legitimate ones. Affected: `NeonRelay` in all three implementations (Java, Python, TypeScript). ### Patches Not yet patched. Fix consists of three changes to handleReconnectRequest in each implementation: 1. Reject the request if `pendingReconnects.size() >= maxPendingConnections` (mirrors the existing connect-flow guard) 2. Only forward to the host if the `sessionId:clientId` key is not already present in `pendingReconnects` — the map entry can still be updated with the new source address, but the host only needs to validate once per slot 3. In `performCleanup`, evict throttled entries before falling back to `rateLimiters.clear()` to avoid resetting legitimate sources' rate limit state ### Workarounds Operators can partially mitigate by placing the relay behind a network-level filter that drops packets with spoofed source addresses (BCP38/uRPF). This does not address the missing `pendingReconnects` size cap or the `rateLimiters.clear()` issue but eliminates the amplification path in most deployment environments. ### References - PROTOCOL.md — reconnect flow - ARCHITECTURE.md — reconnect handshake detail (step 4 describes the unbounded `put`)

Source published

28 Jul 2026 16:36:47 UTC

Source modified

4 Aug 2026 14:40:38 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Publisher rating · HIGH