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CVE-2026-100661— Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation

Quick assessment

Affected
netty netty
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Netty 的 HTTP/3 编解码器（io.netty:netty-codec-http3）在 4.2.0.Final 至 4.2.17.Final 版本中存在拒绝服务（DoS）漏洞，该漏洞位于 QPACK 前缀整数解码器（QpackUtil.decodePrefixedInteger）中，其未对所处理的延续字节（continuation bytes）数量进行上限限制。远程、未认证的对等方可以打开一个 QPACK 单向流（类型为 0x02 编码器或 0x03 解码器），并发送一个所有前缀位均置 1 的首字节（例如

CVSS 7.5 · High EPSS 0.34% · P25
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I. Basic Information for CVE-2026-100661

Vulnerability Information
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Vulnerability Title
Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation
Source: CVE Program / CVE List V5
Vulnerability Description
Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.0.Final through 4.2.17.Final contain a denial-of-service vulnerability in the QPACK prefixed-integer decoder (QpackUtil.decodePrefixedInteger), which does not bound the number of continuation bytes it will process. A remote, unauthenticated peer can open a QPACK unidirectional stream (type 0x02 encoder or 0x03 decoder) and send a first byte with all prefix bits set (e.g. 0xFF for a 7-bit prefix or 0x3F for a 5-bit prefix) followed by an endless run of 0x80 continuation bytes. The decoder returns -1 ('need more bytes'), so callers never consume the input, the ByteToMessageDecoder cumulator grows without bound, and each decode() invocation re-scans the whole accumulated buffer, yielding O(N^2) CPU cost. The result is unbounded per-connection heap growth (OutOfMemoryError) and event-loop CPU starvation, reachable in every configuration. Fixed in 4.2.18.Final.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
netty netty 4.2.0.Final ~ 4.2.18.Final -

II. Public POCs for CVE-2026-100661

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III. Intelligence Information for CVE-2026-100661

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Vendor Advisories for CVE-2026-100661 (1)

Other References for CVE-2026-100661 (1)

Same Patch Batch · netty · 2026-09-26 · 12 CVEs total

CVE-2026-100655 7.5 HIGH Netty before 4.1.138.Final Denial of Service via SpdySessionHandler
CVE-2026-100663 7.5 HIGH Netty HTTP/1 CONNECT authority-form mistranslated to malformed HTTP/3
CVE-2026-100656 7.5 HIGH Netty HttpServerCodec Unbounded Queue Growth via HTTP/1.1 Pipelining
CVE-2026-100660 7.5 HIGH Netty before 4.2.18.Final QpackEncoder Unbounded Memory Retention
CVE-2026-100665 7.5 HIGH Netty 4.2.11 through 4.2.17 QUIC Hostname Verification Bypass
CVE-2026-100662 7.5 HIGH Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS
CVE-2026-100664 7.5 HIGH Netty 4.2.2 through 4.2.17 HTTP/1 Host Header Authority Confusion
CVE-2026-100657 7.5 HIGH Netty before 4.1.138.Final ByteBuf Leak in StompSubframeDecoder
CVE-2026-100666 7.3 HIGH Netty 4.2.0 through 4.2.16 Response Desynchronization via HttpServerCodec
CVE-2026-100659 6.5 MEDIUM Netty 4.2.0 through 4.2.17 HTTP/3 Request Routing Bypass
CVE-2026-100658 5.3 MEDIUM Netty before 4.1.138.Final Denial of Service via WebSocketServerExtensionHandler

IV. Related Vulnerabilities

Same product: netty
Same vendor: netty
Same weakness: CWE-400

V. Comments for CVE-2026-100661

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