# CVE-2026-63344: Refitter: C# source injection through OpenAPI content-type map keys

Status: published. Published: 2026-10-30. Updated: 2026-11-06.

Refitter is a tool for generating a C# REST API client using the Refit library. Prior to 2.1.2, content-type keys in the content maps of `requestBody/responses` are emitted verbatim into a Refit `[Headers("Accept: <ct>", "Content-Type: <ct>")]` attribute string without escaping quotation marks. A crafted content-type key in an attacker-influenced OpenAPI description survives default validation without `--skip-validation`, breaks out of the attribute string and enclosing interface and namespace, and can introduce a top-level file class while leaving valid generated C#. A `[ModuleInitializer]` method in that class executes attacker code when the generated assembly is loaded at application startup, without requiring a call to the client. The behavior was verified with Refitter 2.0.0 and .NET 8. This issue is fixed in version 2.1.2.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- christianhelle / refitter: < 2.1.2 (affected). Source: CNA: GitHub_M
-  / Refitter (Refitter): <= 2.0.0 (affected, GitHub advisory range). Source: GitHub GHSA-p32v-8v8j-j534

## Severity and prioritization

- CVSS 4.0: 8.6 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: GitHub_M

- CVSS 4.0: 8.6 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/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: security-advisories@github.com

- CISA KEV: No listing in collected sources

- EPSS: 0.35% as of 2026-11-06; percentile 28.83%

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

- Weaknesses: CWE-94, CWE-116

## Exploit evidence

- exploit: https://github.com/christianhelle/refitter/security/advisories/GHSA-p32v-8v8j-j534 (ADP: CISA-ADP)

## References

- https://github.com/christianhelle/refitter/security/advisories/GHSA-p32v-8v8j-j534 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/christianhelle/refitter/pull/1178 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/christianhelle/refitter/commit/ab4d8e439d6f0ee82ad49ee15323978d70fe5a67 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/christianhelle/refitter/releases/tag/2.1.2 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/user-attachments/files/29394848/reproduce.sh (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/user-attachments/files/29394851/maintainer-report.txt (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/user-attachments/files/29394853/make_spec.py (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/christianhelle/refitter/security/advisories/GHSA-p32v-8v8j-j534 (ADP: CISA-ADP; exploit)

- https://github.com/christianhelle/refitter/commit/ab4d8e439d6f0ee82ad49ee15323978d70fe5a67 (security-advisories@github.com)

- https://github.com/christianhelle/refitter/pull/1178 (security-advisories@github.com)

- https://github.com/christianhelle/refitter/releases/tag/2.1.2 (security-advisories@github.com)

- https://github.com/christianhelle/refitter/security/advisories/GHSA-p32v-8v8j-j534 (security-advisories@github.com)

- https://github.com/user-attachments/files/29394848/reproduce.sh (security-advisories@github.com)

- https://github.com/user-attachments/files/29394851/maintainer-report.txt (security-advisories@github.com)

- https://github.com/user-attachments/files/29394853/make_spec.py (security-advisories@github.com)

- https://github.com/christianhelle/refitter/security/advisories/GHSA-p32v-8v8j-j534 (GitHub Security Advisories; advisory)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-63344; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63344; retrieved 2026-11-03; source updated 2026-11-02

- GitHub Security Advisories: https://github.com/christianhelle/refitter/security/advisories/GHSA-p32v-8v8j-j534; retrieved 2026-11-04; source updated 2026-07-16

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-63344; retrieved 2026-11-06; source updated Not reported

Revision: 8e7e2005cb18d25ad5d404f08b883a7e7dcd5fac838925102dcaed75f4c17299

Canonical: https://y2.dev/cve/CVE-2026-63344

## 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.