CVE-2026-54428 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in org.apache.httpcomponents.core5:httpcore5-h2. A fix is available for org.apache.httpcomponents.core5:httpcore5-h2 — see the affected versions and patch details below.
Apache HttpComponents Core: HPackDecoder Unlimited Header List Size Before SETTINGS ACK
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54428.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-54428 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 381,682 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
org.apache.httpcomponents.core5:httpcore5-h2☕org.apache.httpcomponents.core5:httpcore5-h2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Allocation of resources without limits or throttling in the HTTP/2 HPACK decoder in Apache HttpComponents Core (5.4.2 and earlier, 5.5-beta1 and earlier) allows an remote attacker to cause a denial of service through memory exhaustion by sending oversized compressed header blocks before the HTTP/2 SETTINGS acknowledgement causes the configured header list size limit to be applied.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.httpcomponents.core5:httpcore5-h2 | all versions | 5.4.3org.apache.httpcomponents.core5:httpcore5-h2:5.4.3 |
| ☕Maven | org.apache.httpcomponents.core5:httpcore5-h2 | ≥ 5.5-alpha1&&< 5.5-beta2 | 5.5-beta2org.apache.httpcomponents.core5:httpcore5-h2:5.5-beta2 |
Affected Products
httpcomponents coreapacheDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.httpcomponents.core5:httpcore5-h2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.apache.httpcomponents.core5:httpcore5-h2 to 5.4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54428 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This is an Important denial of service vulnerability in Apache HttpComponents Core. The HTTP/2 HPACK decoder is susceptible to memory exhaustion when processing oversized compressed header blocks from a remote attacker. This occurs before the system's configured header list size limits are applied, potentially…
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.Source: Red Hat security advisory for CVE-2026-54428 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Cryostat 4 on RHEL 9 | cryostat/cryostat-agent-init-rhel9:0.7.0-12 | RHSA-2026:68333 |
| Red Hat build of Apache Camel 4.18.3 for Spring Boot 3.5.16 | httpcore5-h2 | RHSA-2026:54622 |
| Red Hat build of Quarkus 3.33.2.SP3 | see advisory | RHSA-2026:47172 |
| OpenShift Developer Tools and Services 4.12 | ocp-tools-4/jenkins-rhel8:1786628667 | RHSA-2026:60247 |
| OpenShift Developer Tools and Services 4.13 | ocp-tools-4/jenkins-rhel8:1786628681 | RHSA-2026:60249 |
| OpenShift Developer Tools and Services 4.14 | ocp-tools-4/jenkins-rhel8:1786533561 | RHSA-2026:60248 |
| OpenShift Developer Tools and Services 4.15 | ocp-tools-4/jenkins-rhel8:1786533565 | RHSA-2026:60239 |
| OpenShift Developer Tools and Services 4.16 | ocp-tools-4/jenkins-rhel9:1787125166 | RHSA-2026:60251 |
Frequently Asked Questions
Is CVE-2026-54428 in your dependencies?
Find it across Maven, including transitive dependencies.