CVE-2026-1526High· 7.5▾ TwilightThe undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompr…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 41.3 · likelihood 0.2 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.
Exploit-prediction probability, daily snapshots since Jul 4.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
1.1%
The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompresses incoming compressed frames without enforcing any limit on the decompressed data size. A malicious WebSocket server can send a small compressed frame (a "decompression bomb") that expands to an extremely large size in memory, causing the Node.js process to exhaust available memory and crash or become unresponsive.
The vulnerability exists in the PerMessageDeflate.decompress() method, which accumulates all decompressed chunks in memory and concatenates them into a single Buffer without checking whether the total size exceeds a safe threshold.
undici < 6.24.0undici >= 7.0.0, < 7.24.0Upgrade past the affected range:
undici 7.24.0Connected by shared product, vendor, weakness, or advisory.
CVE-2026-2229High· 7.5ImpactThe undici WebSocket client is vulnerable to a denial-of-service attack due to improper validation of the server_max_window_bits parameter in the permessage-deflate extension
CVE-2026-1528High· 7.5ImpactA server can reply with a WebSocket frame using the 64-bit length form and an extremely large length
CVE-2026-84890Medium· 5.9undici's decompress interceptor decompresses response bodies according to the untrusted Content-Encoding header
CVE-2026-12151High· 7.5undici: undici: Denial of Service due to unbounded memory growth via WebSocket frames (CVE-2026-12151)
CVE-2026-21710High· 7.5A flaw in Node.js HTTP request handling causes an uncaught `TypeError` when a request is received with a header named `__proto__` and the application accesses `req.headersDistinct`. When this occurs, `dest["__proto__"]` resolves to `O…
CVE-2026-18149Medium· 5.9undici's retry handler can leave an already-exposed response body pending forever