# CVE-2026-91147: Cockpit: cockpit: denial of service in `cockpit-ws` due to url-root handling without a trailing slash

Status: published. Published: 2026-09-18. Updated: 2026-11-03.

A flaw was found in `cockpit-ws`. This vulnerability allows a remote, unauthenticated attacker to cause a Denial of Service (DoS) by sending a specially crafted request. When the `WebService.UrlRoot` is configured and a request is made to the exact URL-root prefix without a trailing slash, `cockpit-ws` can terminate unexpectedly. This issue leads to the unavailability of the Cockpit web service.

## Remediation

- workaround: A code fix is being pursued for the affected streams. Until updated packages are available, avoid configuring a non-empty [WebService] UrlRoot in cockpit-ws where feasible. If a non-empty UrlRoot is required, configure the front-end proxy or TLS terminator in front of cockpit-ws to rewrite or redirect requests for the exact configured prefix (for example, /cockpit) to the trailing-slash form (for example, /cockpit/) before forwarding them, so the exact-prefix request never reaches cockpit-ws unnormalized. Deployments whose front end already normalizes or redirects such requests are not exposed through that route. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 8 (cockpit): ≥ 0:310.10-1.el8_10; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10 (cockpit): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (cockpit): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (cockpit): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Dev Spaces (devspaces/udi-base-rhel10): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Dev Spaces (devspaces/udi-base-rhel9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Dev Spaces (devspaces/udi-rhel9): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: 0.40% as of 2026-11-03; percentile 34.70%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-617

## Exploit evidence

- exploit: https://bugzilla.redhat.com/show_bug.cgi?id=2479230 (ADP: CISA-ADP)

## References

- https://access.redhat.com/errata/RHSA-2026:94485 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-91147 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2479230 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2479230 (ADP: CISA-ADP; exploit)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-91147; retrieved 2026-11-03; source updated 2026-11-03

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-91147; retrieved 2026-11-03; source updated Not reported

Revision: ca16ae6c5ff0d6aaca105c282b104fa27deae0bb8edb047cef7959720bd49a92

Canonical: https://y2.dev/cve/CVE-2026-91147

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