CVE-2026-56309: Capgo - Plan Bypass via Unrestricted Attachment Upload Endpoint

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-10 · updated 2026-10-25
Weakness: CWE-770

Description

Capgo before 12.128.2 fails to enforce plan/quota restrictions on the /files/upload/attachments endpoint, allowing plan-blocked apps to create publicly readable R2 objects. Attackers can upload arbitrary attachments using upload-scoped API keys that bypass plan checks, persist outside normal bundle metadata, and survive app deletion, enabling storage and bandwidth abuse.

Affected products

Capgo: before 12.128.2 — fixed in 12.128.2

How to fix

Upgrade to a fixed version: Capgo 12.128.2. Check the vendor advisory for mitigations.

References

https://github.com/Cap-go/capgo/security/advisories/GHSA-q52j-ggvx-cr4v
https://www.vulncheck.com/advisories/capgo-plan-bypass-via-unrestricted-attachment-upload-endpoint
https://github.com/Cap-go/capgo/security/advisories/GHSA-q52j-ggvx-cr4v

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