CVE-2026-31812
ADVISORY - githubSummary
Summary
A remote, unauthenticated attacker can trigger a denial of service in applications using vulnerable quinn versions by sending a crafted QUIC Initial packet containing malformed quic_transport_parameters. In quinn-proto parsing logic, attacker-controlled varints are decoded with unwrap(), so truncated encodings cause Err(UnexpectedEnd) and panic. This is reachable over the network with a single packet and no prior trust or authentication.
Details
The issue is panic-on-untrusted-input in QUIC transport parameter parsing.
In quinn-proto (observed in quinn-proto 0.11.13), parsing of some transport parameters uses a fallible varint decode followed by unwrap(). For malformed/truncated parameter values, decode returns UnexpectedEnd, and unwrap() panics.
Observed output:
thread 'tokio-rt-worker' (2366474) panicked at quinn-proto/src/transport_parameters.rs:473:67:
called `Result::unwrap()` on an `Err` value: UnexpectedEnd
PoC
Reproduces against the upstream Quinn server example.
- Start server:
cargo run --example server -- ./
- Prepare PoC client environment:
python3 -m venv .venv
source .venv/bin/activate
pip install aioquic
- Run PoC script attack.py against server QUIC listener (default example target shown):
python attack.py
Observed output
thread 'tokio-rt-worker' (2366903) panicked at quinn-proto/src/transport_parameters.rs:473:67:
called `Result::unwrap()` on an `Err` value: UnexpectedEnd
Impact
Vulnerability type: Remote Denial of Service (panic/crash)
Attack requirements: Network reachability to UDP QUIC listener
Authentication/privileges: None
Who is impacted: Any server/application using affected quinn/quinn-proto versions where this parse path is reachable; process-level impact depends on integration panic handling policy
This vulnerability was originally submitted by @revofusion to the Ethereum Foundation bug bounty program
GitHub
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CVSS SCORE
8.7high| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| quinn-proto | cargo | - | - | <0.11.14 | 0.11.14 |
CVSS:4 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.
The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges.
There is no loss of confidentiality within the Vulnerable System.
There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
There is no loss of integrity within the Vulnerable System.
There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
NIST
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