Summary
swift-nio-http2 vulnerable to denial of service via mishandled HPACK variable length integer encoding
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. It is fixed in 1.19.2 and later releases.
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.
Impact
An arithmetic operation produces a value that exceeds the integer type's maximum, causing it to wrap to an unexpected small value. Typical impact: incorrect size calculations leading to heap overflows or logic errors.
CVE-2022-24667 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.19.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2022-24667? CVE-2022-24667 is a high-severity integer overflow or wraparound vulnerability in github.com/apple/swift-nio-http2 (swift), affecting versions >= 1.0.0, < 1.19.2. It is fixed in 1.19.2. An arithmetic operation produces a value that exceeds the integer type's maximum, causing it to wrap to an unexpected small value.
- How severe is CVE-2022-24667? CVE-2022-24667 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/apple/swift-nio-http2 are affected by CVE-2022-24667? github.com/apple/swift-nio-http2 (swift) versions >= 1.0.0, < 1.19.2 is affected.
- Is there a fix for CVE-2022-24667? Yes. CVE-2022-24667 is fixed in 1.19.2. Upgrade to this version or later.
- Is CVE-2022-24667 exploitable, and should I be worried? Whether CVE-2022-24667 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2022-24667 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2022-24667? Upgrade
github.com/apple/swift-nio-http2to 1.19.2 or later.