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Denial of service via HTTP/2 HEADERS frames padding

High severity GitHub Reviewed Published Mar 10, 2022 in apple/swift-nio-http2 • Updated Feb 9, 2024

Package

swift github.com/apple/swift-nio-http2 (Swift)

Affected versions

>= 1.0.0, < 1.20

Patched versions

1.20

Description

A program using swift-nio-http2 is vulnerable to a denial of service attack, caused by a network peer sending a specially crafted HTTP/2 frame. This attack affects all swift-nio-http2 versions from 1.0.0 to 1.19.2. It is fixed in 1.20.0 and later releases.

This vulnerability is caused by a logical error when parsing a HTTP/2 HEADERS or HTTP/2 PUSH_PROMISE frame where the frame contains padding information without any other data. This logical error caused confusion about the size of the frame, leading to a parsing error. This parsing error immediately crashes the entire process.

Sending a HEADERS frame or PUSH_PROMISE frame with HTTP/2 padding information does not require any special permission, so any HTTP/2 connection peer may send such a frame. For clients, this means any server to which they connect may launch this attack. For servers, anyone they allow to connect to them may launch such an attack.

The attack is low-effort: it takes very little resources to send an appropriately crafted frame. The impact on availability is high: receiving the frame immediately crashes the server, dropping all in-flight connections and causing the service to need to restart. It is straightforward for an attacker to repeatedly send appropriately crafted frames, so attackers require very few resources to achieve a substantial denial of service.

The attack does not have any confidentiality or integrity risks in and of itself: swift-nio-http2 is parsing the frame in memory-safe code, so the crash is safe. However, sudden process crashes can lead to violations of invariants in services, so it is possible that this attack can be used to trigger an error condition that has confidentiality or integrity risks.

The risk can be mitigated if untrusted peers can be prevented from communicating with the service. This mitigation is not available to many services.

The issue is fixed by rewriting the parsing code to correctly handle the condition. The issue was found by automated fuzzing by oss-fuzz.

References

@Lukasa Lukasa published to apple/swift-nio-http2 Mar 10, 2022
Published by the National Vulnerability Database Mar 10, 2022
Published to the GitHub Advisory Database Jun 9, 2023
Reviewed Jun 9, 2023
Last updated Feb 9, 2024

Severity

High

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 v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

0.179%
(56th percentile)

Weaknesses

No CWEs

CVE ID

CVE-2022-0618

GHSA ID

GHSA-q36x-r5x4-h4q6

Source code

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