SEPTEMBER 19, 2026
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Case File

CVE-2026-45623

HIGH · CVSS 7.5 EPSS 0.59% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-07-27 · Last synced 2026-08-26

CyberRota Analysis

AI-Generated

Oracle's PostCSS versions 8.5.11 and earlier are vulnerable to a file leakage issue due to improper handling of source mapping comments in CSS files, allowing attackers to read arbitrary files from the local filesystem. This vulnerability can lead to sensitive data exposure and potential denial-of-service attacks when untrusted CSS is processed. Organizations using PostCSS in environments where user-uploaded styles or third-party CSS are processed should prioritize upgrading to version 8.5.12 to mitigate this risk.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

GitHub PoC Links

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-45623
Severity
HIGH
CVSS
7.5
EPSS
0.59%
Oracle

Original NVD Description

PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. In versions 8.5.11 and prior, the PreviousMap parses the /*# sourceMappingURL=PATH */ comment from any CSS string passed to process() and dereferences PATH against the local filesystem with no scheme, allowlist, or traversal check. An attacker who controls the CSS input can cause the host process to read any file readable by Node and leak the first ~10 bytes of its content through the resulting JSON.parse SyntaxError message. The bug also yields a precise file-existence oracle and a controllable-read primitive that may be combined with large-file targets for DoS. The behaviour is triggered with PostCSS's default options — no from, no map, no plugins required — and is therefore reachable from any pipeline that runs untrusted CSS through PostCSS (CMS themes, user-uploaded styles, browser-extension/userstyle processors, build pipelines for third-party packages, blog comment renderers, etc.). This issue has been fixed in version 8.5.12.

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