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… (CVE-2026-100661)
Netty's HTTP/3 codec versions 4.2.0.Final through 4.2.17.Final have a denial-of-service vulnerability in the QPACK prefixed-integer decoder. The decoder does not limit the number of continuation bytes it processes, allowing a remote unauthenticated attacker to cause unbounded memory growth and CPU exhaustion. This leads to OutOfMemoryError and event-loop CPU starvation. The vulnerability is fixed in version 4.2.18.Final.
AI Analysis
Technical Summary
The vulnerability exists in the QPACK prefixed-integer decoder (QpackUtil.decodePrefixedInteger) of Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.0.Final through 4.2.17.Final. The decoder does not limit the number of continuation bytes it processes. An attacker can open a QPACK unidirectional stream (type 0x02 encoder or 0x03 decoder) and send a first byte with all prefix bits set followed by an endless sequence of 0x80 continuation bytes. The decoder repeatedly returns -1 indicating it needs more bytes, causing the ByteToMessageDecoder cumulator to grow without bound. Each decode invocation rescans the entire buffer, resulting in O(N^2) CPU usage, unbounded heap growth, and eventual OutOfMemoryError and CPU starvation. This affects every configuration and is fixed in version 4.2.18.Final.
Potential Impact
A remote, unauthenticated attacker can exploit this vulnerability to cause a denial-of-service condition by exhausting memory and CPU resources on the affected system. This leads to application crashes (OutOfMemoryError) and event-loop CPU starvation, impacting availability. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade to Netty HTTP/3 codec version 4.2.18.Final or later where this vulnerability is fixed. No other mitigations are indicated or effective.
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… (CVE-2026-100661)
Description
Netty's HTTP/3 codec versions 4.2.0.Final through 4.2.17.Final have a denial-of-service vulnerability in the QPACK prefixed-integer decoder. The decoder does not limit the number of continuation bytes it processes, allowing a remote unauthenticated attacker to cause unbounded memory growth and CPU exhaustion. This leads to OutOfMemoryError and event-loop CPU starvation. The vulnerability is fixed in version 4.2.18.Final.
CVSS v3.1
Score 7.5high
Affected software
pkg:maven/io.netty/netty-codec-http3Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability exists in the QPACK prefixed-integer decoder (QpackUtil.decodePrefixedInteger) of Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.0.Final through 4.2.17.Final. The decoder does not limit the number of continuation bytes it processes. An attacker can open a QPACK unidirectional stream (type 0x02 encoder or 0x03 decoder) and send a first byte with all prefix bits set followed by an endless sequence of 0x80 continuation bytes. The decoder repeatedly returns -1 indicating it needs more bytes, causing the ByteToMessageDecoder cumulator to grow without bound. Each decode invocation rescans the entire buffer, resulting in O(N^2) CPU usage, unbounded heap growth, and eventual OutOfMemoryError and CPU starvation. This affects every configuration and is fixed in version 4.2.18.Final.
Potential Impact
A remote, unauthenticated attacker can exploit this vulnerability to cause a denial-of-service condition by exhausting memory and CPU resources on the affected system. This leads to application crashes (OutOfMemoryError) and event-loop CPU starvation, impacting availability. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade to Netty HTTP/3 codec version 4.2.18.Final or later where this vulnerability is fixed. No other mitigations are indicated or effective.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-7m86-g9j9-26xf
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-100661"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6ab89be2f7a7c54106942064
Added to database: 09/27/2026, 04:30:26 UTC
Last enriched: 09/27/2026, 04:43:57 UTC
Last updated: 09/28/2026, 01:47:40 UTC
Views: 19
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