Skip to content

qcp has possible crash/DOS in some build configurations

Moderate severity GitHub Reviewed Published Mar 7, 2025 in crazyscot/qcp • Updated Mar 8, 2025

Package

cargo qcp (Rust)

Affected versions

< 0.3.3

Patched versions

0.3.3

Description

Nature of issue: Crash (Denial of Service)
Source of issue: Dependent package (ring)
Affected versions of qcp: 0.1.0-0.3.2
Recommendation: Upgrade to qcp 0.3.3 or later

Who is affected

All versions of qcp from 0.1.0 to 0.3.2 are affected, but only if built with runtime overflow checks.

  • Released qcp binaries do not enable runtime overflow checks by default. If you use an official released qcp binary download, you are not affected.
  • If you built qcp yourself in debug mode, you are affected unless your debug configuration explicitly disables overflow checks.
  • If you built qcp yourself in release mode, you are only affected if you explicitly requested runtime overflow checks at build time by setting the appropriate RUSTFLAGS, or in your Cargo.toml profile.

What to do if you are affected

We recommend you upgrade to qcp 0.3.3 or later.
Users upgrading from versions prior to 0.3.0 should note that an incompatible protocol change was introduced in version 0.3.0, so should stage their upgrade carefully.

Alternatively, it is possible to avoid upgrading by rebuilding qcp locally. The following alternative mitigations have been identified:

  • Rebuild locally with runtime overflow checks disabled
  • Rebuild locally using a fixed version of the ring dependency (0.17.12 or later).

Detail

The upstream advisory describes a crash in the implementation of the QUIC protocol that can be induced by a specially-crafted packet, and which happens naturally approximately every 1 in 2**32 packets sent and/or received.

The crash only happens when runtime overflow checking is enabled. Note that the upstream advisory describes the overflow check causing this issue as "unwanted". Their response, to remove the overflow check in one place, does not introduce any additional issue.

Impact

During qcp file transfer sessions, it is possible for an attacker to send a specially-crafted packet that could trigger this issue.

  • In that case, and only if qcp was built with runtime overflow checks enabled, the effect is a Rust panic which immediately aborts the transfer. There is no additional impact on system resources at either end, nor on other file transfers in progress.
  • As qcp runs a separate process for every connected user, the impact of the attack is limited to a single session.

The underlying issue may also affect particularly large file transfers. The maximum TLS packet size is 16KB, so 2**32 packets will transfer up to 68TB (including the protocol/retransmit overhead). Again, this is only the case if qcp was built with runtime overflow checks enabled.

As of the time of writing, we are not aware of any reports of this issue being exploited.

Additional notes

  • The qcp protocol itself does not rely on runtime overflow checks for its security.
  • While QUIC servers are normally public-facing, qcp is a hybrid protocol that first requires an authenticated ssh session in order to set up the QUIC session. The window of attackability is therefore reduced, though will depend on your usage profile.
  • An additional layer of obscurity is provided by qcp using ephemeral, random port numbers for its QUIC traffic (subject to user configuration).

References

Upstream advisories:

References

@crazyscot crazyscot published to crazyscot/qcp Mar 7, 2025
Published to the GitHub Advisory Database Mar 8, 2025
Reviewed Mar 8, 2025
Last updated Mar 8, 2025

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 None
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:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

EPSS score

Weaknesses

No CWEs

CVE ID

No known CVE

GHSA ID

GHSA-fmwf-c46w-r8qm

Source code

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