Bug 2541889 (CVE-2026-100661)
| Summary: | CVE-2026-100661 io.netty/netty-codec-http3: Netty: Denial of Service via unbounded accumulation in QPACK integer decoder | ||
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| Product: | [Other] Security Response | Reporter: | OSIDB Bzimport <bzimport> |
| Component: | vulnerability | Assignee: | Product Security DevOps Team <prodsec-dev> |
| Status: | NEW --- | QA Contact: | |
| Severity: | high | Docs Contact: | |
| Priority: | high | ||
| Version: | unspecified | CC: | sdawley |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
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| Fixed In Version: | Doc Type: | --- | |
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A flaw was found in Netty's HTTP/3 codec. A remote, unauthenticated attacker can cause a Denial of Service (DoS) by sending a specially crafted stream of data to the QPACK integer decoder. Because the decoder fails to limit incoming continuation bytes, data accumulates indefinitely in memory while repeatedly rescanning the buffer. This unbounded accumulation can exhaust system memory and consume excessive CPU resources, rendering the service unresponsive.
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| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
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| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
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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.