PostCSS 8.5.18: SourceMap Leakage via PreviousMap.loadFile()
CVE-2026-69153 Published on August 3, 2026
PostCSS: incomplete fix of CVE-2026-45623 — attacker-controlled sourceMappingURL reads arbitrary .map files when `from` is unset
PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. Prior to 8.5.19, if from is unset, an attacker can cause PreviousMap.loadFile() to read an unintended source-map file by supplying an absolute or directory-traversal sourceMappingURL. The resulting maps sources and sourcesContent may then be exposed to the application. This issue is fixed in version 8.5.19.
Vulnerability Analysis
CVE-2026-69153 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. Public availability of a proof of concept (POC) exploit exists for CVE-2026-69153. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Types
What is a Directory traversal Vulnerability?
The software uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the software does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
CVE-2026-69153 has been classified to as a Directory traversal vulnerability or weakness.
What is an Information Disclosure Vulnerability?
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
CVE-2026-69153 has been classified to as an Information Disclosure vulnerability or weakness.
Products Associated with CVE-2026-69153
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