PatchSiren cyber security CVE debrief

CVE-2026-56306 Capgo CVE debrief

CVE-2026-56306 is a medium-severity vulnerability in Capgo, a product of Unknown Vendor, which has a weak parsing vulnerability in the x-limited-key-id header. This vulnerability allows remote attackers to bypass subkey enforcement by submitting malformed values, zero, or duplicate headers that result in NaN or falsy values. As a result, attackers can manipulate the x-limited-key-id header to disable limited key scoping and execute requests using the main API key context instead of restricted subkey permissions. The vulnerability has a CVSS score of 5.3 and was published on June 22, 2026. The CVE record was last modified on June 23, 2026.

Vendor: Capgo
Product: Unknown
CVSS: MEDIUM 5.3
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-06-22
Original CVE updated: 2026-06-23
Advisory published: 2026-06-22
Advisory updated: 2026-06-23

Who should care

Security teams and administrators responsible for Capgo installations should be aware of this vulnerability. Given the medium severity and potential for exploitation, defenders should prioritize assessment and remediation efforts. Organizations using Capgo should verify their installations and update to a patched version if available.

Technical summary

The vulnerability exists in the x-limited-key-id header parsing mechanism of Capgo. Specifically, the code fails to properly handle malformed or duplicate headers, leading to NaN or falsy values. Attackers can exploit this weakness to bypass subkey enforcement, allowing them to execute requests with elevated privileges. The vulnerability is characterized by a CVSS:4.0 vector of AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/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.

Defensive priority

Defenders should prioritize patching or mitigating this vulnerability in their Capgo installations. Given the medium severity, it is essential to assess the risk and implement compensating controls if a patch is not immediately available.

Recommended defensive actions

Assess Capgo installations for vulnerability to CVE-2026-56306
Update Capgo to version 12.128.2 or later if available
Implement compensating controls to restrict access to the x-limited-key-id header
Monitor for suspicious activity related to the x-limited-key-id header
Verify API key usage and subkey permissions

Evidence notes

The CVE record and NVD detail provide official information about the vulnerability. Additional sources, including Vulncheck and GitHub advisories, offer further context and potential mitigations. However, the exact scope of affected Capgo installations and the vendor's remediation workflow are not explicitly stated in the provided sources.

Official resources

This article is AI-assisted and based on the supplied source corpus.