Skip to content

arnika is affected by medium-severity issues in UDP rotation, PQC handling, and KMS TLS

Moderate severity GitHub Reviewed Published May 11, 2026 in arnika-project/arnika • Updated May 15, 2026

Package

gomod github.com/arnika-project/arnika (Go)

Affected versions

<= 1.0.0

Patched versions

None

Description

Summary

Three medium-severity issues in arnika affecting the UDP key-rotation protocol, PQC key file handling, and KMS TLS client. All require specific preconditions to exploit and do not allow direct code execution or immediate key extraction. A self-contained PoC is attached.

Details

  1. ACK timestamp not validated: udpserver.go:185
    udpClient() verifies HMAC and packet type but never checks ackPkt.Timestamp. A MITM can capture one ACK, drop all subsequent DATA packets, and replay the stale ACK indefinitely. Primary advances PSK each rotation, backup stays on key 1, tunnel breaks. No PSK knowledge needed. The server side already has this check, the client does not.
    Fix: mirror the timestamp check already present on the server side.

  2. Empty PQC key file silently accepted: repositories/pqc.go:29
    os.ReadFile follows symlinks. Empty file to base64.Decode("") = []byte{}, nil. HKDF runs on the QKD key alone while arnika logs [OK] HKDF derivation completed for QKD+PQC key. Requires write access to the directory containing PQC_PSK_FILE.
    Fix: validate decoded key is non-empty before derivation; enforce parent directory permissions in SECURITY.md.

  3. InsecureSkipVerify: true hardcoded: repositories/kms.go:61
    KMS HTTP client unconditionally sets InsecureSkipVerify: true, overriding RootCAs. CA_CERTIFICATE is loaded but never consulted (dead code). Requires MITM between arnika and the KMS endpoint, which in typical deployments are co-located.
    Fix: remove the flag; RootCAs already holds the correct pool when CA_CERTIFICATE is configured.

PoC

See arnika_exploit.tar.gz. PoC shows observable behavior for each attack; the third one (KMS MITM) needs no custom code, any HTTPS proxy with a self-signed cert is enough.

Impact

Issues require network MITM or local directory write access to exploit. No direct key extraction or code execution. Primary impact is tunnel desync and silent security downgrade in hybrid QKD+PQC mode.

Patch

This issue has been fixed by the 1.0.1 release: https://github.com/arnika-project/arnika/releases/tag/v1.0.1.

References

@nean-and-i nean-and-i published to arnika-project/arnika May 11, 2026
Published to the GitHub Advisory Database May 15, 2026
Reviewed May 15, 2026
Last updated May 15, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements Present
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity None
Availability Low
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

EPSS score

Weaknesses

Authentication Bypass by Capture-replay

A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). Learn more on MITRE.

Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate. Learn more on MITRE.

Insufficient Verification of Data Authenticity

The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-rc6v-5rmx-w5mv

Source code

Credits

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.