CVE-2026-4923 — path-to-regexp
MEDIUMCVE-2026-4923 is a medium-severity (CVSS 5.9) CWE-1333 vulnerability in path-to-regexp. A fix is available for path-to-regexp — see the affected versions and patch details below.
path-to-regexp vulnerable to Regular Expression Denial of Service via multiple wildcards
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-4923.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-4923 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
path-to-regexpnpmDescription
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 developers are using multiple wildcard parameters, they can check the regex output with a tool such as https://makenowjust-labs.github.io/recheck/playground/ to confirm whether a path is vulnerable.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | path-to-regexp | ≥ 8.0.0&&< 8.4.0 | 8.4.0npm install path-to-regexp@8.4.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for path-to-regexp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update path-to-regexp to 8.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-4923 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-4923 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-4923. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Developer Hub 1.10 | rhdh/rhdh-hub-rhel9:1780930740 | RHSA-2026:24841 |
Frequently Asked Questions
Is CVE-2026-4923 in your dependencies?
O3 Security finds CVE-2026-4923 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.