CVE-2025-59530 is a high-severity (CVSS 7.5) Reachable Assertion 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 has Client Crash Due to Premature HANDSHAKE_DONE Frame
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-2025-59530.
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-2025-59530 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 377,636 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-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
Summary
A misbehaving or malicious server can trigger an assertion in a quic-go client (and crash the process) by sending a premature HANDSHAKE_DONE frame during the handshake.
Impact
A misbehaving or malicious server can cause a denial-of-service (DoS) attack on the quic-go client by triggering an assertion failure, leading to a process crash. This requires no authentication and can be exploited during the handshake phase. Observed in the wild with certain server implementations (e.g. Solana's Firedancer QUIC).
Affected Versions
- All versions prior to v0.49.1 (for the 0.49 branch)
- Versions v0.50.0 to v0.54.0 (inclusive)
- Fixed in v0.49.1, v0.54.1, and v0.55.0 onward
Users are recommended to upgrade to the latest patched version in their respective maintenance branch or to v0.55.0 or later.
Details
For a regular 1-RTT handshake, QUIC uses three sets of keys to encrypt / decrypt QUIC packets:
- Initial keys (derived from a static key and the connection ID)
- Handshake keys (derived from the client's and server's key shares in the TLS handshake)
- 1-RTT keys (derived when the TLS handshake finishes)
On the client side, Initial keys are discarded when the first Handshake packet is sent. Handshake keys are discarded when the server's HANDSHAKE_DONE frame is received, as specified in section 4.9.2 of RFC 9001. Crucially, Initial keys are always dropped before Handshake keys in a standard handshake.
Due to packet reordering, it is possible to receive a packet with a higher encryption level before the key for that encryption level has been derived. For example, the server's Handshake packets (containing, among others, the TLS certificate) might arrive before the server's Initial packet (which contains the TLS ServerHello). In that case, the client queues the Handshake packets and decrypts them as soon as it has processed the ServerHello and derived Handshake keys.
After completion of the handshake, Initial and Handshake packets are not needed anymore and will be dropped. quic-go implements an assertion that no packets are queued after completion of the handshake.
A misbehaving or malicious server can trigger this assertion, and thereby cause a panic, by sending a HANDSHAKE_DONE frame before actually completing the handshake. In that case, Handshake keys would be dropped before Initial keys.
This can only happen if the server implementation is misbehaving: the server can only complete the handshake after receiving the client's TLS Finished message (which is sent in Handshake packets).
The Fix
quic-go needs to be able to handle misbehaving server implementations, including those that prematurely send a HANDSHAKE_DONE frame. We now discard Initial keys when receiving a HANDSHAKE_DONE frame, thereby correctly handling premature HANDSHAKE_DONE frames. The fix was implemented in https://github.com/quic-go/quic-go/pull/5354.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/quic-go/quic-go | all versions | 0.49.1go get github.com/quic-go/quic-go@v0.49.1 |
| 🐹Go | github.com/quic-go/quic-go | ≥ 0.50.0&&< 0.54.1 | 0.54.1go get github.com/quic-go/quic-go@v0.54.1 |
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 0.49.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-59530 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-2025-59530 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-59530. 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.
The availability risk is limited to applications which includethe quic-go library. Host Red Hat systems are not at risk of availability degradation.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ansible Automation Platform 2.4 for RHEL 8 | receptor-0:1.6.2-1.el8ap | RHSA-2025:21706 |
| Red Hat Ansible Automation Platform 2.5 for RHEL 8 | ansible-builder-0:3.1.1-1.el8ap | RHSA-2025:23069 |
| Red Hat Ansible Automation Platform 2.6 for RHEL 9 | receptor-0:1.6.2-2.el9ap | RHSA-2025:21768 |
| Red Hat Advanced Cluster Management for Kubernetes 2.13 | rhacm2/lighthouse-agent-rhel9:1782924920 | RHSA-2026:36873 |
| Red Hat Advanced Cluster Management for Kubernetes 2.14 | rhacm2/lighthouse-agent-rhel9:v0.21-1762794425 | RHSA-2025:21892 |
| Red Hat Advanced Cluster Management for Kubernetes 2.15 | rhacm2/lighthouse-agent-rhel9:v0.22-1764857716 | RHSA-2025:22784 |
| Red Hat Ansible Automation Platform 2.5 | ansible-automation-platform-25/receptor-rhel8:1.6 | RHSA-2025:23131 |
| Red Hat Ansible Automation Platform 2.6 | ansible-automation-platform-26/ee-supported-rhel9:1.0 | RHSA-2025:21775 |
Frequently Asked Questions
Is CVE-2025-59530 in your dependencies?
O3 Security finds CVE-2025-59530 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.