Highest advisory severityHigh 2 vendors · 2 advisories

CVE-2026-55833

Denial of Service via SPDY header decompression amplification

CVE-2026-55833: Denial of Service via SPDY header decompression amplification. Not in the CISA KEV catalog. High advisory severity (CVSS 7.5, Red Hat).

Compare the source-linked records below. Ratings and product/version details belong to each advisory; they are not a single CVE-wide score or proof that every listed product is affected. How VulniPulse collects and checks evidence.

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CVE-2026-55833 key facts

CISA KEV: Not listed (catalog checked Nov 6, 2026)
Highest advisory severity: High
CVSS base score: 7.5 (Red Hat)
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (Red Hat)
Weakness: CWE-409
Fixed releases: Red Hat: 4.1.136, 4.2.16, cryostat/cryostat-reports-rhel9:4.2.0-14, cryostat/cryostat-rhel9:4.2.0-14, cryostat/jfr-datasource-rhel9:4.2.0-14, netty-codec-http and 44 more in the advisory
Vendor advisories: 2 from NetApp, Red Hat
VulniPulse record: Published Jul 28, 2026 · Updated Sep 29, 2026

Scores, vectors, weaknesses and fixed releases are quoted from vendor advisories that cover only CVE-2026-55833; bulletin-wide values are not repeated here.

Is CVE-2026-55833 exploited?

No exploitation is reported in the sources VulniPulse tracks: CVE-2026-55833 is not in the CISA KEV catalog (checked Nov 6, 2026) and no tracked advisory for it reports exploitation. That is not proof the vulnerability cannot be exploited.

How do I fix CVE-2026-55833?

Upgrade to a fixed release named by the vendor:

Red Hat: 4.1.136, 4.2.16, cryostat/cryostat-reports-rhel9:4.2.0-14, cryostat/cryostat-rhel9:4.2.0-14, cryostat/jfr-datasource-rhel9:4.2.0-14, netty-codec-http

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. (Red Hat)

Vendor advisory comparison

NetApp

1 advisory

Advisory severityHigh8.1
High [CVE-2026-44249 +6] September 2026 IBM Db2 Netty Vulnerabilities in NetApp Products
NTAP-20260917-0005Source published Sep 17, 2026Source updated Sep 29, 2026
This bulletin covers 7 CVEs. The products, versions, score and guidance below describe the bulletin; check its source for applicability to this specific CVE.
IBM Db2 Server 11.5.0 through 11.5.9 on Linux x86-64 are susceptible to vulnerabilities in Netty open source libraries. Successful exploitation of these vulnerabilities could lead to disclosure of sensitive information, addition or modification of data, or Denial of Service (DoS). NetApp states there is no workaround available at this time.
Affected products in this advisory
No product details extracted. Check the source bulletin.
Source-reported affected versions
11.5.0
11.5.9
Source-reported fixed versions
No fixed-version detail extracted. This does not mean no fix exists.
Mitigation guidance
No mitigation guidance extracted; consult the source.
Full advisory and evidence Open source bulletin

Red Hat

1 advisory

Advisory severityHigh7.5
High [CVE-2026-55833] Denial of Service via SPDY header decompression amplification
CVE-2026-55833Source published Jul 20, 2026Source updated Jul 20, 2026
Netty is a network application framework for development of protocol servers and clients. Prior to 4.1.136.Final and 4.2.16.Final, Netty SPDY header decoding continues inflating zlib-compressed header blocks after the raw header parser has exceeded `maxHeaderSize` and marked the frame truncated in `SpdyFrameCodec`, allowing a remote peer to send a small compressed `HEADERS` block that expands into much larger raw header data and causes compression-amplified CPU and allocation churn. By sending a specially crafted, small compressed header block, the attacker can cause it to expand significantly during decompression, leading to excessive CPU usage and memory allocation. This can result in a denial of service (DoS) due to resource exhaustion. This is an Important denial of service…
Affected products in this advisory
Cryostat 4 on RHEL 9
Red Hat AMQ Broker 7.13.6
Red Hat AMQ Broker 7.14.1
Red Hat build of Apache Camel 4.18.3 for Spring Boot 3.5.16
23 more entries in the full advisory.
Source-reported affected versions
< 4.1.136.Final
< 4.2.16.Final
Source-reported fixed versions
4.1.136
4.2.16
cryostat/cryostat-reports-rhel9:4.2.0-14
cryostat/cryostat-rhel9:4.2.0-14
46 more entries in the full advisory.
Mitigation guidance
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Full advisory and evidence Open source bulletin

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