No exploitation reportedFix available

CVE-2026-4923

Q: Is CVE-2026-4923 actively exploited?

Active exploitation of CVE-2026-4923 has not been confirmed. Its EPSS score was 0.4% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2026-4923?

CVE-2026-4923 has a CVSS v3 base score of 5.9 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

No exploitation reported by the sources we read.

Published2026-03-26
Fixed in8.4.0
WeaknessCWE-1333

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Impact: When using multiple wildcards, combined with at least one parameter, a regular expression can be generated that is vulnerable to ReDoS. This backtracking vulnerability requires the second wildcard to be somewhere other than the end of the path. Unsafe examples: /*foo-*bar-:baz /*a-:b-*c-:d /x/*a-:b/*c/y Safe examples: /*foo-:bar /*foo-:bar-*baz Patches: Upgrade to version 8.4.0. Workarounds: If you are using multiple wildcard parameters, you can check the regex output with a tool such as https://makenowjust-labs.github.io/recheck/playground/ to confirm whether a path is vulnerable.

Timeline

dates in UTC

2026-03-2619:17CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-4923?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-4923?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV

Pillarjs path-to-regexp

Branch	Affected	Fixed in	Source
8.x	≥ 8.0.0, < 8.4.0	8.4.0	NVD · OSV

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Pillarjs path-to-regexp to 8.4.0

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVE recordread 2026-10-23
CISA-ADPSSVC decisionnone2026-03-27
OpenCVESSVC decisionnone—
CNACVSS 3.15.9read 2026-10-23
CNAweakness (CWE)CWE-1333read 2026-10-23
FIRST EPSSEPSS score0.4 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2026-03-26
Last Modified: 2026-06-17
NVD status: Analyzed

Frequently asked questions

What is CVE-2026-4923?

Is CVE-2026-4923 actively exploited?

Active exploitation of CVE-2026-4923 has not been confirmed. Its EPSS score was 0.4% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-4923?

CVE-2026-4923 has a CVSS v3 base score of 5.9 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

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