### 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: ```java if (blockedStreamsCount == maxBlockedStreams - 1) { ``` If the server enables QPACK dynamic tables (by setting `HTTP3_SETTINGS_QPACK_MAX_TABLE_CAPACITY` > 0) but does not explicitly configure `HTTP3_SETTINGS_QPACK_BLOCKED_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.
### 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: ```java if (blockedStreamsCount == maxBlockedStreams - 1) { ``` If the server enables QPACK dynamic tables (by setting `HTTP3_SETTINGS_QPACK_MAX_TABLE_CAPACITY` > 0) but does not explicitly configure `HTTP3_SETTINGS_QPACK_BLOCKED_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.
Update io.netty:netty-codec-http3 to 4.2.15.Final if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanNetty HTTP/3 QPACK Blocked Streams Memory Exhaustion affects io.netty:netty-codec-http3 (maven). Severity is high. ### 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: ```java if (blockedStreamsCount == maxBlockedStreams - 1) { ``` If the server enables QPACK dynamic tables (by setting `HTTP3_SETTINGS_QPACK_MAX_TABLE_CAPACITY` > 0) but does not explicitly configure `HTTP3_SETTINGS_QPACK_BLOCKED_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.
AI coding agents often install or upgrade packages automatically in maven. A high vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| io.netty:netty-codec-http3maven | >=4.2.0.Final,<=4.2.13.Final | 4.2.15.Final |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL GuardUpdate io.netty:netty-codec-http3 to 4.2.15.Final if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanNetty HTTP/3 QPACK Blocked Streams Memory Exhaustion affects io.netty:netty-codec-http3 (maven). Severity is high. ### 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: ```java if (blockedStreamsCount == maxBlockedStreams - 1) { ``` If the server enables QPACK dynamic tables (by setting `HTTP3_SETTINGS_QPACK_MAX_TABLE_CAPACITY` > 0) but does not explicitly configure `HTTP3_SETTINGS_QPACK_BLOCKED_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.
AI coding agents often install or upgrade packages automatically in maven. A high vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| io.netty:netty-codec-http3maven | >=4.2.0.Final,<=4.2.13.Final | 4.2.15.Final |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL Guard