Answer in brief
CVE-2026-9675 records a High severity (CVSS 7.5) vulnerability in undici WebSocket client vulnerable to denial of service via cumulative fragment bypass. The current sources do not mark it as known exploited. The current feed maps undici (npm). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps undici (npm). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| undicinpm | >=8.0.0,<8.5.0 | 8.5.0 |
Published upstream
Jun 17, 2026
Evidence: source:ghsa:source_dates:source-dates:recordSource modified
Oct 22, 2026
Evidence: source:ghsa:source_dates:source-dates:recordFirst seen by HOL
Jun 19, 2026
## Impact The undici WebSocket client enforces `maxPayloadSize` per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious WebSocket server can stream many small fragments that each pass per-frame validation but collectively exceed the configured limit, causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service. Affected applications are those using the undici WebSocket client (`new WebSocket(...)`) that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint. This is a regression specific to undici 8.1.0. The 6.25.0 line shipped the equivalent cumulative check from the start and is unaffected. The 7.x line never had the `maxPayloadSize` feature and is also unaffected. ## Patches Upgrade to undici >= 8.5.0. ## Workarounds No workaround is available. The fix must be applied through an upgrade.
Quoted source text, attributed separately from HOL analysis.