CVE-2026-59881
Description
A flaw was found in AIOHTTP. The WebSocket client in AIOHTTP processes compressed data frames even when the compression mechanism, known as permessage-deflate, has not been properly negotiated. A malicious server can exploit this by sending specially crafted compressed frames. This can lead to unexpected and excessive consumption of the system's central processing unit (CPU) and memory, potentially resulting in a denial of service (DoS) for legitimate users.
Statement
Red Hat rates this flaw as Moderate with a CVSS score of 5.3 because exploitation requires an aiohttp WebSocket client to connect to an attacker-controlled server. In typical Red Hat product deployments, aiohttp serves as an HTTP client library for internal service communication rather than establishing WebSocket connections to untrusted endpoints. The resulting resource consumption is limited to the individual process running the affected client and does not propagate to other services or the host system.
Mitigation
For deployments where upgrading is not immediately possible, ensure that aiohttp WebSocket clients only connect to trusted servers. The vulnerability requires the client to have opted out of permessage-deflate compression and the server to send RSV1-flagged frames, so connections using default compression settings are less likely to trigger this issue.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | N/A | N/A |
| Attack Vector | Network | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | None | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | Low | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Amplification; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
System resources, CPU and memory, can be quickly consumed. This can lead to poor system performance or system crash.
Frequently Asked Questions
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