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CVE-2026-4867— path-to-regexp vulnerable to Regular Expression Denial of Service via multiple route parameters

Quick assessment

Affected
path-to-regexp path-to-regexp
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Path-to-RegExp是pillarjs开源的一个工具。用于将路径字符串转换为正则表达式。 path-to-regexp 0.1.12及之前版本存在安全漏洞，该漏洞源于生成的正则表达式存在缺陷，可能导致正则表达式拒绝服务。

CVSS 7.5 · High EPSS 0.50% · P40

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking
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I. Basic Information for CVE-2026-4867

Vulnerability Information
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Vulnerability Title
path-to-regexp vulnerable to Regular Expression Denial of Service via multiple route parameters
Source: CVE Program / CVE List V5
Vulnerability Description
Impact: A bad regular expression is generated any time you have three or more parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b-:c or /:a-:b-:c-:d. The backtrack protection added in path-to-regexp@0.1.12 only prevents ambiguity for two parameters. With three or more, the generated lookahead does not block single separator characters, so capture groups overlap and cause catastrophic backtracking. Patches: Upgrade to path-to-regexp@0.1.13 Custom regex patterns in route definitions (e.g., /:a-:b([^-/]+)-:c([^-/]+)) are not affected because they override the default capture group. Workarounds: All versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b-:c to /:a-:b([^-/]+)-:c([^-/]+). If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1333
Source: CVE Program / CVE List V5
Vulnerability Title
Path-to-RegExp 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Path-to-RegExp是pillarjs开源的一个工具。用于将路径字符串转换为正则表达式。 path-to-regexp 0.1.12及之前版本存在安全漏洞，该漏洞源于生成的正则表达式存在缺陷，可能导致正则表达式拒绝服务。
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
path-to-regexp path-to-regexp 0 ~ 0.1.13 -

II. Public POCs for CVE-2026-4867

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III. Intelligence Information for CVE-2026-4867

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Vendor Advisories for CVE-2026-4867 (1)

Security Blog Posts for CVE-2026-4867 (1)

Same Patch Batch · path-to-regexp · 2026-03-26 · 3 CVEs total

CVE-2026-4926 7.5 HIGH path-to-regexp vulnerable to Denial of Service via sequential optional groups
CVE-2026-4923 5.9 MEDIUM path-to-regexp vulnerable to Regular Expression Denial of Service via multiple wildcards

IV. Related Vulnerabilities

Same product: path-to-regexp
Same vendor: path-to-regexp
Same weakness: CWE-1333

V. Comments for CVE-2026-4867

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