# CVE-2026-123201: buku through 5.1.1 SSRF via bukuserver fetch_data and network_handle API

Status: published. Published: 2026-11-05. Updated: 2026-11-09.

Buku (bukuserver) through 5.1.1 contains an unauthenticated server-side request forgery vulnerability that allows remote attackers to make the server request internal hosts by supplying a url parameter to /api/fetch_data or /api/network_handle. Attackers can target loopback, private, or cloud metadata IP addresses, which pass the weak is_bad_url() check and follow redirects, to discover internal services and read their page titles, descriptions, and keywords.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/jarun/buku/pull/916
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/jarun/buku/commit/13f6497afc974f02f1069b760772abe8815d1675

## Affected products and versions

- jarun / buku (buku): ≥ 0; ≤ 5.1.1 (affected, custom). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N; source: CNA: VulnCheck

- CVSS 4.0: 6.3 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.39% as of 2026-11-09; percentile 33.91%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-918

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/jarun/buku/issues/910 (CNA: VulnCheck; issue-tracking)

- https://github.com/jarun/buku/pull/916 (CNA: VulnCheck; patch, issue-tracking)

- https://github.com/jarun/buku/commit/13f6497afc974f02f1069b760772abe8815d1675 (CNA: VulnCheck; patch)

- https://github.com/jarun/buku/blob/e232ac357cbba22fe69d6d6dfc0d35512a4cd313/bukuserver/api.py#L97-L105 (CNA: VulnCheck; technical-description)

- https://github.com/jarun/buku/blob/e232ac357cbba22fe69d6d6dfc0d35512a4cd313/buku.py#L4057-L4084 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/buku-through-5.1.1-ssrf-via-bukuserver-fetch-data-and-network-handle-api (CNA: VulnCheck; third-party-advisory)

- https://github.com/jarun/buku/blob/e232ac357cbba22fe69d6d6dfc0d35512a4cd313/buku.py#L4057-L4084 (disclosure@vulncheck.com)

- https://github.com/jarun/buku/blob/e232ac357cbba22fe69d6d6dfc0d35512a4cd313/bukuserver/api.py#L97-L105 (disclosure@vulncheck.com)

- https://github.com/jarun/buku/commit/13f6497afc974f02f1069b760772abe8815d1675 (disclosure@vulncheck.com)

- https://github.com/jarun/buku/issues/910 (disclosure@vulncheck.com)

- https://github.com/jarun/buku/pull/916 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/buku-through-5.1.1-ssrf-via-bukuserver-fetch-data-and-network-handle-api (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-123201; retrieved 2026-11-09; source updated 2026-11-09

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123201; retrieved 2026-11-06; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-123201; retrieved 2026-11-09; source updated Not reported

Revision: 8d628da5233a7471ecbdf3cc244fe871f6d472ab32343ea8767128bf8b9b8696

Canonical: https://y2.dev/cve/CVE-2026-123201

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.