CVE-2022-24667 swift-nio-http2 vulnerable to denial of service via mishandled HPACK variable length integer encoding

What is CVE-2022-24667?

CVE-2022-24667 is a high-severity denial of service vulnerability in SwiftNIO HTTP2, published on 9 Feb 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

A program using swift-nio-http2 is vulnerable to a denial of service attack, caused by a network peer sending a specially crafted HPACK-encoded header block. This attack affects all swift-nio-http2 versions from 1.0.0 to 1.19.1. There are a number of implementation errors in the parsing of HPACK-encoded header blocks that allow maliciously crafted HPACK header blocks to cause crashes in processes using swift-nio-http2. Each of these crashes is triggered instead of an integer overflow. A malicious HPACK header block could be sent on any of the HPACK-carrying frames in a HTTP/2 connection (HEADERS and PUSH_PROMISE), at any position. Sending a HPACK header block does not require any special permission, so any HTTP/2 connection peer may send one. 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 field block. The impact on availability is high: receiving a frame carrying this field block 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 field blocks, 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 field block in memory-safe code and the crash is triggered instead of an integer overflow. 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 all conditions in the function. The principal issue was found by automated fuzzing by oss-fuzz, but several associated bugs in the same code were found by code audit and fixed at the same time

Weakness: CWE-190

Which versions are affected by CVE-2022-24667?

2 open source packages ship an affected version, including github.com/apple/swift-nio-http2. It affects 1 product.

Products include Apple Swiftnio Http\/2.

How do I fix CVE-2022-24667?

Upgrade github.com/apple/swift-nio-http2 to 1.19.2 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2022-24667 being exploited?

There is no known exploitation of CVE-2022-24667 in the wild and no public exploit code.

Other vulnerabilities in SwiftNIO HTTP2

• CVE-2022-0618 Denial of service via HTTP/2 HEADERS frames padding High 7.5
• CVE-2022-24666 swift-nio-http2 vulnerable to denial of service via invalid HTTP/2 HEADERS frame length High 7.5
• CVE-2022-24668 swift-nio-http2 vulnerable to denial of service via ALTSVC or ORIGIN frames High 7.5
• CVE-2026-64785 swift-nio-http2: Missing CR/LF/NUL validation in header values Medium 5.3
• CVE-2026-28898 SwiftNIO HTTP/2: HTTP/2-to-HTTP/1 Request Smuggling via unvalidated :path pseudo-header in HTTP2ToHTTP1Codec Medium 5.3

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-w3f6-pc54-gfw7.