Apache HttpComponents Core: HPackDecoder Unlimited Header List Size Before SETTINGS ACK

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-54428: 0.87% estimated exploitation activity in the next 30 days; percentile 58.90 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

1 Jul 2026, 18:31 UTC

Last modified by the source

13 Aug 2026, 18:27 UTC

Source last checked

26 Oct 2026, 16:54 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-v3jc-474w-2wm6

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# Patch Next advisory brief: CVE-2026-54428

Advisory: Apache HttpComponents Core: HPackDecoder Unlimited Header List Size Before SETTINGS ACK
IDs: CVE-2026-54428, GHSA-v3jc-474w-2wm6
Record: https://patchnext.com/advisories/cve-2026-54428 (revision 1, source checked 26 Oct 2026, 16:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.apache.httpcomponents.core5:httpcore5-h2 5.5-beta2, 5.4.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.apache.httpcomponents.core5:httpcore5-h2: affected < 5.4.3; >= 5.5-alpha1, < 5.5-beta2; fixed in 5.4.3, 5.5-beta2

## Suggested inspection (read-only)
- Maven org.apache.httpcomponents.core5:httpcore5-h2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.apache.httpcomponents.core5:httpcore5-h2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-v3jc-474w-2wm6 (GitHub-reviewed advisory GHSA-v3jc-474w-2wm6 lists affected ranges: Maven org.apache.httpcomponents.core5:httpcore5-h2 >=0 =5.5-alpha1 <5.5-beta2)

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