# CVE-2026-121737: CVE-2026-121737

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

When a remote, unauthenticated HTTP/1.1 client pipelined the start of a second request and then stopped reading, proxygen's coroutine-based HTTP session could free that pipelined stream while resetting the connection's streams on the resulting write timeout, then go on to use it. This can crash the server, leading to denial of service, and may allow memory corruption with further impact. This issue affects proxygen versions prior to v2026.11.09.00.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Facebook / proxygen: ≥ v0.0.0.0; < v2026.11.09.00 (affected, semver). Source: CNA: Meta

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-416

## Exploit evidence

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

## References

- https://www.facebook.com/security/advisories/cve-2026-121737 (CNA: Meta; x_refsource_CONFIRM)

- https://github.com/meta/proxygen/commit/daf245bba7fe1304b9491403fe56f91153299781 (CNA: Meta; x_refsource_MISC)

- https://github.com/meta/proxygen/commit/daf245bba7fe1304b9491403fe56f91153299781 (cve-assign@fb.com)

- https://www.facebook.com/security/advisories/cve-2026-121737 (cve-assign@fb.com)

## Provenance

- CNA: Meta: https://www.cve.org/CVERecord?id=CVE-2026-121737; retrieved 2026-11-11; source updated 2026-11-11

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121737; retrieved 2026-11-11; source updated 2026-11-11

Revision: 9ebed69ab633c006e15e9eb9a962ab751dc1de0eb0ec8d3e1f8e9504bd8245f5

Canonical: https://y2.dev/cve/CVE-2026-121737

## 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.

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- 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.