ALAS2-2025-2856


Amazon Linux 2 Security Advisory: ALAS2-2025-2856
Advisory Released Date: 2025-05-29
Advisory Updated Date: 2025-05-29
Severity: Important

Issue Overview:

Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, `Rack::QueryParser` parses query strings and `application/x-www-form-urlencoded` bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters. The vulnerability arises because `Rack::QueryParser` iterates over each `&`-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing. An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may use middleware to enforce a maximum query string size or parameter count, or employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies. Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation. (CVE-2025-46727)


Affected Packages:

pcs


Note:

This advisory is applicable to Amazon Linux 2 (AL2) Core repository. Visit this FAQ section for the difference between AL2 Core and AL2 Extras advisories.


Issue Correction:
Run yum update pcs to update your system.

New Packages:
aarch64:
    pcs-0.9.169-3.amzn2.3.0.6.aarch64
    pcs-snmp-0.9.169-3.amzn2.3.0.6.aarch64
    pcs-debuginfo-0.9.169-3.amzn2.3.0.6.aarch64

i686:
    pcs-0.9.169-3.amzn2.3.0.6.i686
    pcs-snmp-0.9.169-3.amzn2.3.0.6.i686
    pcs-debuginfo-0.9.169-3.amzn2.3.0.6.i686

src:
    pcs-0.9.169-3.amzn2.3.0.6.src

x86_64:
    pcs-0.9.169-3.amzn2.3.0.6.x86_64
    pcs-snmp-0.9.169-3.amzn2.3.0.6.x86_64
    pcs-debuginfo-0.9.169-3.amzn2.3.0.6.x86_64