# CVE-2026-121560: LogChimp before 0.9.3 Authorization Bypass via PATCH /api/v1/posts

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

LogChimp 0.9.0-alpha.1 before 0.9.3 contains an authorization bypass vulnerability that allows authenticated post authors to modify any other post by supplying mismatched postId and id body parameters. Attackers can set postId to their own post and id to an enumerated victim post UUID to overwrite its title, slug, content, boardId and roadmap_id.

## 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/logchimp/logchimp/commit/a78b69af342908472ad400285187e43729295a7c

## Affected products and versions

- logchimp / logchimp (logchimp/logchimp): ≥ 0.9.0-alpha.1; < 0.9.3 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 7.1 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 7.1 (high); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L; source: CNA: VulnCheck

- CVSS 4.0: 7.1 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/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: 7.1 (high); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

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

- Weaknesses: CWE-639

## Exploit evidence

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

## References

- https://github.com/logchimp/logchimp/commit/a78b69af342908472ad400285187e43729295a7c (CNA: VulnCheck; patch)

- https://github.com/logchimp/logchimp (CNA: VulnCheck; product)

- https://github.com/logchimp/logchimp/blob/v0.9.2/packages/server/src/controllers/post/updatePost.ts#L67 (CNA: VulnCheck; technical-description)

- https://github.com/logchimp/logchimp/blob/v0.9.2/packages/server/src/middlewares/postExists.ts#L72-L77 (CNA: VulnCheck; technical-description)

- https://github.com/logchimp/logchimp/releases/tag/v0.9.3 (CNA: VulnCheck; technical-description, release-notes)

- https://www.vulncheck.com/advisories/logchimp-before-0.9.3-authorization-bypass-via-patch-api-v1-posts (CNA: VulnCheck; third-party-advisory)

- https://github.com/logchimp/logchimp (disclosure@vulncheck.com)

- https://github.com/logchimp/logchimp/blob/v0.9.2/packages/server/src/controllers/post/updatePost.ts#L67 (disclosure@vulncheck.com)

- https://github.com/logchimp/logchimp/blob/v0.9.2/packages/server/src/middlewares/postExists.ts#L72-L77 (disclosure@vulncheck.com)

- https://github.com/logchimp/logchimp/commit/a78b69af342908472ad400285187e43729295a7c (disclosure@vulncheck.com)

- https://github.com/logchimp/logchimp/releases/tag/v0.9.3 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/logchimp-before-0.9.3-authorization-bypass-via-patch-api-v1-posts (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121560; retrieved 2026-11-03; source updated 2026-11-03

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121560; retrieved 2026-11-03; source updated 2026-11-03

Revision: b632b7a2a117e7d4a8e31281e8aa0469c2906db854c1990e29d245263d1dc37b

Canonical: https://y2.dev/cve/CVE-2026-121560

## 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.