> CVE-2026-93575

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PUBLISHED
2026-09-18 11:17
MODIFIED
2026-09-18 11:17
EPSS (Prob. Exploit)
0.39%
Top 68.7%
DATA SOURCES:
NVD 🔗 2026-09-18 FIRST EPSS 🔗 2026-10-18

> DESCRIPTION

### Summary Netty's fix for CVE-2026-44248 is incomplete. The decoder checks if the MQTT packet's `Remaining Length` exceeds `maxBytesInMessage`, but fails to validate the `Properties Length` against the `Remaining Length`. An attacker can bypass the size limit by sending a small `Remaining Length` but an enormous `Properties Length`. This forces Netty to buffer and parse millions of properties, allowing an unauthenticated remote attacker to trigger excessive memory and CPU consumption, leading to OutOfMemoryError. ### Details In `io.netty.handler.codec.mqtt.MqttDecoder`, the `decodeProperties()` helper method reads `totalPropertiesLength` and attempts to parse that many bytes. If the buffer lacks the full length, a `Signal` is thrown. The `catch` block inside `decode()` only enforces `maxBytesInMessage` against `bytesRemainingBeforeVariableHeader` (the packet's `Remaining Length`). By sending a `CONNECT` packet with a small `Remaining Length` but a huge `Properties Length`, the size check passes. `ReplayingDecoder` then buffers data from the network until the huge `Properties Length` is reached, parsing millions of `UserProperty` objects and exhausting CPU and memory. #

> AFFECTED_PRODUCTS

ℹ️ Aucun produit affecté n'a encore été publié par NVD pour cette CVE.

> WEAKNESSES

CWE-1035

> HISTORIQUE DES MODIFICATIONS

Première apparition
18/09/2026 11:17
Source: NVD
Total des modifications: 0 Dernière mise à jour: 1 month ago

> REFERENCES

https://access.redhat.com/security/cve/CVE-2026-93575
https://bugzilla.redhat.com/show_bug.cgi?id=2536967
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