CVE-2026-126073
Description
A flaw was found in Action Pack. When determining response formats through content negotiation, Action Pack fails to properly set or append to the HTTP Vary response header under certain request conditions. A remote attacker can exploit this behavior by sending requests through a shared intermediary cache, causing the cache to store an improperly formatted response. This leads to web cache poisoning, where subsequent users receive unexpected response representations, such as HTML instead of JSON or unstyled web pages.
Statement
This vulnerability is rated as Moderate impact because successful exploitation requires specific deployment prerequisites—namely, fronting the application with a shared caching proxy while serving public responses that rely on content negotiation—and does not allow an attacker to inject arbitrary content. Under default configurations, typical Red Hat deployments do not expose publicly cacheable, content-negotiated endpoints to shared intermediate caches without explicit application design. Because an attacker cannot control the cached data beyond inducing the proxy to serve an unintended valid representation to subsequent clients, the blast radius is restricted to minor presentation discrepancies or temporary format mismatches.
Mitigation
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.
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 | 4.8 | N/A | 4.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L
Understanding the Weakness (CWE)
Other
Technical Impact: Quality Degradation; Varies by Context
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