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CVE-2026-73646— PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure

Quick assessment

Affected
postcss postcss
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

PostCSS是PostCSS组织开源的一个使用 JavaScript 转换 CSS 的工具。 PostCSS 8.5.18之前版本存在路径遍历漏洞，该漏洞源于loadMap()和loadFile()函数对sourceMappingURL和.map文件路径验证不当，可能导致攻击者通过result.map泄露任意可访问.map文件中的sourcesContent。

CVSS 7.5 · High EPSS 0.53% · P43

Possible ATT&CK Techniques 1 AI

T1005 · Data from Local System

Affected Version Matrix 1

VendorProduct Version RangeStatus
postcss postcss < 8.5.18 affected
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I. Basic Information for CVE-2026-73646

Vulnerability Information
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Vulnerability Title
PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure
Source: CVE Program / CVE List V5
Vulnerability 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. Prior to 8.5.18, lib/previous-map.js loadMap() passes attacker-controlled sourceMappingURL values to join(dirname(opts.from), annotation), and loadFile() permits traversed or absolute .map paths, allowing untrusted CSS processed without map: false to disclose sourcesContent from arbitrary reachable .map files through result.map. This issue is fixed in version 8.5.18.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5
Vulnerability Title
PostCSS 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
PostCSS是PostCSS组织开源的一个使用 JavaScript 转换 CSS 的工具。 PostCSS 8.5.18之前版本存在路径遍历漏洞，该漏洞源于loadMap()和loadFile()函数对sourceMappingURL和.map文件路径验证不当，可能导致攻击者通过result.map泄露任意可访问.map文件中的sourcesContent。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
postcss postcss < 8.5.18 -

II. Public POCs for CVE-2026-73646

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
Success marker: VULNERABLE: sourceMappingURL traversal read /secret/app-secret.map and disclosed its sourcesContent (PROOF_052c20c92c70e3b5) through result.map
Reproduction recording is a Pro+ exclusive
Watch the full sandbox build + live exploit recording for this CVE. Limited-time ¥499/mo.
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claude_code · 9719 chars
GitHub 复现环境（可 clone 直接跑）
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III. Intelligence Information for CVE-2026-73646

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Patches & Fixes for CVE-2026-73646 (1)

Vendor Advisories for CVE-2026-73646 (1)

Vendor Pages for CVE-2026-73646 (1)

IV. Related Vulnerabilities

Same product: postcss
Same vendor: postcss
Same weakness: CWE-22

V. Comments for CVE-2026-73646

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