CVE-2026-55553 is a high-severity (CVSS 7.5) Information Exposure vulnerability. O3 Security confirms whether CVE-2026-55553 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
urllib is an HTTP client for Node.js that supports authentication, redirects, timeouts, and other request features. Prior to 4.9.1 and 2.44.1, urllib follows redirects through followRedirect…
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55553.
Description
urllib is an HTTP client for Node.js that supports authentication, redirects, timeouts, and other request features. Prior to 4.9.1 and 2.44.1, urllib follows redirects through followRedirect but reuses caller-supplied options across origins. In src/HttpClient.ts, #requestInternal recursively calls this.#requestInternal(nextUrl.href, options, requestContext), causing options.headers and auth or digestAuth values to be reused when the redirect target has a different scheme, host, or port. Authorization, Cookie, Proxy-Authorization, x-api-key, x-auth-token, and x-access-token can therefore be sent to an attacker-controlled redirected origin, exposing credentials intended for the original origin and potentially allowing reuse against the original partner API or related services. No user interaction is required. This issue is fixed in versions 2.44.1 and 4.9.1.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-55553 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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 pinpoints whether CVE-2026-55553 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-55553. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-55553 in your dependencies?
O3 detects CVE-2026-55553 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.