CVE-2026-49349 in regclient
Summary
by MITRE • 08/12/2026
regclient is a Docker and OCI Registry Client in Go. Prior to version 0.11.5, credentials for a registry may be inadvertently leaked to external servers. A prerequisite for this attack is a malicious registry server, a malicious blob store, or a registry that does not restrict the external URLs for foreign blobs. Version 0.11.5 fixes the issue.
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Analysis
by VulDB Data Team • 08/12/2026
The regclient project represents a significant security vulnerability in Docker and OCI registry operations that could lead to credential exposure across network boundaries. This flaw exists in versions prior to 0.11.5 where the client application fails to properly validate or restrict external URL references during registry operations. The vulnerability stems from inadequate input validation mechanisms that allow malicious actors to manipulate registry interactions, potentially causing the client to inadvertently transmit authentication credentials to unauthorized external endpoints. Such credential leakage represents a critical compromise of security controls that protect containerized environments from unauthorized access.
The technical implementation of this vulnerability involves the improper handling of foreign blob references within the registry protocol communication. When regclient encounters external blob references during registry operations, it fails to validate whether these references originate from trusted sources or if they point to malicious endpoints. This lack of validation creates an attack surface where a malicious registry server can craft responses that include external URLs pointing to attacker-controlled infrastructure. The client then proceeds to make additional requests to these external endpoints without proper credential sanitization, potentially exposing sensitive authentication tokens, access keys, or other registry credentials. This issue directly relates to CWE-20, which addresses improper input validation, and falls under the broader category of insecure data handling in network communications.
The operational impact of this vulnerability extends beyond simple credential exposure to encompass potential compromise of entire container registries and associated infrastructure. Attackers exploiting this flaw could gain unauthorized access to private repositories, potentially leading to supply chain attacks where malicious images are pushed to legitimate registries. The vulnerability's requirement for a malicious registry server or compromised blob store indicates that it operates in environments where trust assumptions may have been violated, but the client itself fails to provide adequate protection mechanisms. This represents a failure of defense-in-depth principles where the client should not rely entirely on the integrity of external endpoints.
Mitigation strategies must address both the immediate code-level fixes and broader architectural considerations for secure registry operations. The patch implemented in version 0.11.5 corrects the credential handling behavior by enforcing stricter validation of external blob references and ensuring that authentication data is properly isolated during cross-domain communications. Organizations should immediately upgrade to version 0.11.5 or later to remediate this vulnerability, while also implementing network-level controls such as firewall rules that restrict outbound connections from registry clients to known trusted endpoints. The solution aligns with ATT&CK technique T1566 which covers credential harvesting through malicious external connections. Additionally, security teams should conduct comprehensive audits of their container registry configurations and implement monitoring for unusual external URL patterns in registry communications to detect potential exploitation attempts before they succeed.