CVE-2023-49295 is a medium-severity (CVSS 6.4) Uncontrolled Resource Consumption vulnerability in github.com/quic-go/quic-go. A fix is available for github.com/quic-go/quic-go — see the affected versions and patch details below.
quic-go's path validation mechanism can cause denial of service
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-49295.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-49295 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/quic-go/quic-go🐹github.com/quic-go/quic-go🐹github.com/quic-go/quic-go🐹github.com/quic-go/quic-goReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/quic-go/quic-go | ≥ 0.40.0&&< 0.40.1 | 0.40.1go get github.com/quic-go/quic-go@v0.40.1 |
| 🐹Go | github.com/quic-go/quic-go | ≥ 0.39.0&&< 0.39.4 | 0.39.4go get github.com/quic-go/quic-go@v0.39.4 |
| 🐹Go | github.com/quic-go/quic-go | ≥ 0.38.0&&< 0.38.2 | 0.38.2go get github.com/quic-go/quic-go@v0.38.2 |
| 🐹Go | github.com/quic-go/quic-go | all versions | 0.37.7go get github.com/quic-go/quic-go@v0.37.7 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/quic-go/quic-go, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/quic-go/quic-go to 0.40.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-49295 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-49295 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-49295. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ansible Automation Platform 2.4 for RHEL 8 | receptor-0:1.4.4-1.el8ap | RHSA-2024:0855 |
Frequently Asked Questions
Is CVE-2023-49295 in your dependencies?
O3 Security finds CVE-2023-49295 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.