CVE-2026-48748 is a high-severity allocation of resources without limits or throttling vulnerability in io.netty:netty-codec-http3 (maven), affecting versions >= 4.2.0.Final, <= 4.2.13.Final. It is fixed in 4.2.15.Final.
Summary A memory exhaustion vulnerability in the Netty HTTP/3 codec allows the creation of an infinite number of blocked streams, which can cause OOM error. Details The vulnerability exists in io.netty.handler.codec.http3.QpackDecoder#shouldWaitForDynamicTableUpdates: If a client sends a header referencing a table entry that the server hasn't received yet, the server must pause that stream and wait for the missing entry to arrive. To prevent attackers from exhausting resources by intentionally sending missing references, Netty limits the number of streams that can be blocked at the same time. However, the check is implemented as: If the server enables QPACK dynamic tables (by setting HTTP3SETTINGSQPACKMAXTABLECAPACITY > 0) but does not explicitly configure HTTP3SETTINGSQPACKBLOCKED_STREAMS, it defaults to 0. When maxBlockedStreams is 0, the condition evaluates to blockedStreamsCount == -1. Since blockedStreamsCount starts at 0 and only increments, it never equals -1. This bypasses the limit, allowing an attacker to open an infinite number of streams that block indefinitely. Additionally, the QpackDecoder never removes unblocked streams from the blockedStreams map or decrements the counter, meaning the ReadResumptionListener for each blocked stream is kept in memory for the entire lifetime of the connection. This exhausts server memory and crashes the JVM. Impact Denial of Service. Any server using netty-codec-http3 with QPACK dynamic tables enabled and maxBlockedStreams defaulting to 0 is impacted.
The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.
CVE-2026-48748 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (4.2.15.Final). Upgrading removes the vulnerable code path.
maven
io.netty:netty-codec-http3 (>= 4.2.0.Final, <= 4.2.13.Final)io.netty:netty-codec-http3 → 4.2.15.Final (maven)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Upgrade io.netty:netty-codec-http3 to 4.2.15.Final or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-48748 is a high-severity allocation of resources without limits or throttling vulnerability in io.netty:netty-codec-http3 (maven), affecting versions >= 4.2.0.Final, <= 4.2.13.Final. It is fixed in 4.2.15.Final. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
CVE-2026-48748 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
io.netty:netty-codec-http3 (maven) versions >= 4.2.0.Final, <= 4.2.13.Final is affected.
Yes. CVE-2026-48748 is fixed in 4.2.15.Final. Upgrade to this version or later.
Whether CVE-2026-48748 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade io.netty:netty-codec-http3 to 4.2.15.Final or later.