CVE-2026-45623Public exploitNetwork attack vector

Local file disclosure via unchecked sourceMappingURL path

Published Jul 27, 2026 · Updated Jul 27, 2026

Path traversal in PostCSS 8.5.11 and earlier allows remote attackers to read local files through CSS containing a sourceMappingURL. PreviousMap extracts the comment path and loadMap passes it to loadFile, which resolves traversal segments and reads the target synchronously without an allowlist. Exploitation requires attacker-controlled CSS to reach process(); exposed errors leak about 10 file bytes, while path-dependent responses reveal file existence.

CVSS severity7.5
High
EPSS probability0.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in PostCSS 8.5.11 and earlier allows remote attackers to read local files through CSS containing a sourceMappingURL. PreviousMap extracts the comment path and loadMap passes it to loadFile, which resolves traversal segments and reads the target synchronously without an allowlist. Exploitation requires attacker-controlled CSS to reach process(); exposed errors leak about 10 file bytes, while path-dependent responses reveal file existence.

The record

CVE
CVE-2026-45623
Published
Jul 27, 2026
Updated
Jul 27, 2026
Vendor
PostCSS
Product
PostCSS
Classifications
CWE-200, CWE-22, T1005, T1083
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 8.5.12

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PostCSS · PostCSSversion=< 8.5.12

Published CVSS scores

9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1005Data from Local System
T1083File and Directory Discovery

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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