CVE-2026-4867: Impact: A bad regular expression is generated any time you have three or more parameters within a single segm

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HIGH 7.5REMOTEUPGRADE

CVE-2026-4867 is a high-severity flaw (CVSS 7.5) affecting path-to-regexp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 backtrack

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 56%)
CISA exploited list	No
Weakness	CWE-1333
Published	2026-03-26
Last modified	2026-06-17

Publisher (CNA): openjs · Vendor: pillarjs

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-26 17:16 UTCPublished CVE record published
2026-06-17 10:57 UTCUpdated Record last modified

pillarjs path-to-regexp UPGRADE

Affected: < 0.1.13

Fixed in: 0.1.13

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls path-to-regexp

2. UPGRADE to 0.1.13

npm install path-to-regexp@">=0.1.13"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-4867?

path-to-regexp: upgrade to 0.1.13. Exact commands for each OS are on this page.

Is CVE-2026-4867 being exploited?

CVE-2026-4867 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-4867 affect?

CVE-2026-4867 affects path-to-regexp. Severity is high (CVSS 7.5). 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 pa

How urgent is CVE-2026-4867?

Priority 42/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-4926 HIGH 7.5 UPGRADE Impact: A bad regular expression is generated any time you have multiple sequential optional groups (curly br
CVE-2026-4923 MEDIUM 5.9 UPGRADE Impact: When using multiple wildcards, combined with at least one parameter, a regular expression can be gene

References

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