Apache HttpComponents Core 5.4.2: HTTP/2 HPACK Decoder Memory DoS
CVE-2026-54428 Published on July 1, 2026
Apache HttpComponents Core: HPackDecoder Unlimited Header List Size Before SETTINGS ACK
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.
Vulnerability Analysis
CVE-2026-54428 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Types
Allocation of Resources Without Limits or Throttling
The software allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.
What is a Resource Exhaustion Vulnerability?
The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
CVE-2026-54428 has been classified to as a Resource Exhaustion vulnerability or weakness.
Affected Versions
Apache Software Foundation Apache HttpComponents Core:- Version 5.5-alpha, <= 5.5-beta1 is affected.
- Version 5.0-alpha, <= 5.4.2 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.