CVE-2026-9358
Description
A flaw was found in postcss. A remote attacker could exploit a vulnerability in the toString function of the AST Serialization component by executing a manipulation, leading to uncontrolled recursion. This uncontrolled recursion can result in a Denial of Service (DoS) condition, making the affected system unavailable.
Statement
Moderate: This flaw in Postcss can lead to a denial of service (DoS) in applications that process untrusted CSS. The vulnerability arises from uncontrolled recursion in the AST Serialization component when handling specially crafted CSS. Exploitation requires user interaction, such as submitting attacker-controlled CSS, which reduces the risk in environments where CSS is typically pre-compiled or not directly user-modifiable.
Mitigation
Upgrade to PostCSS 8.5.6 or later. As a workaround, validate and sanitize CSS input before processing with PostCSS to prevent deeply nested or malicious structures from reaching the serializer.
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.3 | N/A | 4.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
Red Hat CVSS v3 Score Explanation
Aligned with CVEORG v3.1 assessment. DoS via uncontrolled recursion requires user interaction (processing attacker-supplied CSS). Low availability impact.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Resources including CPU, memory, and stack memory could be rapidly consumed or exhausted, eventually leading to an exit or crash.
Confidentiality
Technical Impact: Read Application Data
In some cases, an application's interpreter might kill a process or thread that appears to be consuming too much resources, such as with PHP's memory_limit setting. When the interpreter kills the process/thread, it might report an error containing detailed information such as the application's installation path.
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