CVE-2023-49295

An attacker can cause its peer to run out of memory sending a large number of PATH_CHALLENGE frames. The receiver is supposed to respond to each PATH_CHALLENGE frame with a PATH_RESPONSE frame. The attacker can prevent the receiver from sending out (the vast majority of) these PATH_RESPONSE frames by collapsing the peers congestion window (by selectively acknowledging received packets) and by manipulating the peer's RTT estimate.

I published a more detailed description of the attack and its mitigation in this blog post: https://seemann.io/posts/2023-12-18-exploiting-quics-path-validation/

There's no way to mitigate this attack, please update quic-go to a version that contains the fix.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2023-49295 has a CVSS score of 6.4 (Medium). The vector is network-reachable, low 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 (0.40.1, 0.39.4, 0.38.2, 0.37.7); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2023-49295? CVE-2023-49295 is a medium-severity uncontrolled resource consumption vulnerability in github.com/quic-go/quic-go (go), affecting versions = 0.40.0. It is fixed in 0.40.1, 0.39.4, 0.38.2, 0.37.7. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2023-49295? CVE-2023-49295 has a CVSS score of 6.4 (Medium). 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.
3. Which versions of github.com/quic-go/quic-go are affected by CVE-2023-49295? github.com/quic-go/quic-go (go) versions = 0.40.0 is affected.
4. Is there a fix for CVE-2023-49295? Yes. CVE-2023-49295 is fixed in 0.40.1, 0.39.4, 0.38.2, 0.37.7. Upgrade to this version or later.
5. Is CVE-2023-49295 exploitable, and should I be worried? Whether CVE-2023-49295 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
6. What actually determines whether CVE-2023-49295 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.
7. How do I fix CVE-2023-49295?
   • Upgrade github.com/quic-go/quic-go to 0.40.1 or later
   • Upgrade github.com/quic-go/quic-go to 0.39.4 or later
   • Upgrade github.com/quic-go/quic-go to 0.38.2 or later
   • Upgrade github.com/quic-go/quic-go to 0.37.7 or later