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How CVE-2026-10740 Works
s2n-quic is a Rust implementation of the QUIC protocol. An unauthenticated user can attempt to exhaust server memory on an s2n-quic endpoint by sending crafted CRYPTO frames with high offsets. The buffer used for processing CRYPTO frames does not enforce a maximum size. In the worst case, a single 1200-byte packet can cause approximately 9.4 MB of allocation. By repeatedly sending such packets, the resulting memory pressure could cause denial of service. No valid handshake is required. The vulnerability originates from an unbounded memory allocation in the CRYPTO frame reassembler of s2n-quic. An unauthenticated remote actor can transmit specially crafted QUIC Initial packets that trigger repeated allocation of memory without bounds, leading to exhaustion of system resources. This manifests as a denial of service, degrading the availability of the affected service. The weakness corresponds to uncontrolled memory allocation, classified under CWE‑770. The affected product is AWS s2n‑quic. All released versions prior to 1.82.0 are vulnerable. The fix is included in version 1.82.0 and later. The CVSS score of 5.3 (CVSS:3.1) / 6.9 (CVSS:4.0) reflects a Medium severity. The likely attack vector is remote and unauthenticated. If successful, the attacker can force the target to allocate excessive memory, consuming resources and causing service interruption.
DailyCVE Form:
Platform: s2n-quic (AWS)
Version: <= v1.81.0
Vulnerability: CWE-770
Severity: Medium (CVSS 5.3/6.9)
Date: 06/10/2026
Prediction: Upgrade to v1.82.0
What Undercode Say:
Analytics of CVE-2026-10740
Check s2n-quic version cargo tree | grep s2n-quic Check for vulnerable versions cargo tree | grep "s2n-quic v"
Simulate memory allocation pattern (Educational) A single 1200-byte packet can cause ~9.4 MB allocation Formula: offset fragment_size = memory allocation High offset values trigger unbounded allocation Example of crafted CRYPTO frame with high offset offset: 0xFFFFFFFF, length: 1200 bytes Result: ~9.4 MB allocation per packet
Monitor memory usage
watch -n 1 'ps aux | grep s2n-quic'
Check for anomalous memory spikes
while true; do ps aux | grep s2n-quic | awk "{print \$6}"; sleep 1; done
Exploit: (Educational Purposes!)
Attack Vector: Remote, Unauthenticated
Prerequisites: None (no valid handshake required)
Mechanism:
- Attacker sends crafted QUIC Initial packets with CRYPTO frames containing high offset values
- The CRYPTO frame reassembler allocates memory based on the offset without enforcing a maximum size
- Each 1200-byte packet triggers ~9.4 MB of memory allocation
- Repeated packets exhaust server memory, causing denial of service
Impact: Degraded availability of the affected service
Protection:
Primary Mitigation:
- Upgrade s2n-quic to version v1.82.0 or later
Secondary Mitigations:
- Block or throttle QUIC traffic from external sources to limit the rate of incoming Initial packets
- Configure the application or infrastructure to monitor memory consumption and alert when anomalous spikes occur
Workarounds:
- There is no workaround that fully mitigates this issue
Impact:
Technical Impact: Unbounded memory allocation in the CRYPTO frame reassembler
Business Impact: Denial of service (degraded availability)
Attack Complexity: Low (easy exploitability)
Authentication: None required
CVSS Score: 5.3 (CVSS:3.1) / 6.9 (CVSS:4.0) – Medium severity
Affected Versions: All s2n-quic versions prior to 1.82.0
Remediation: Upgrade to version 1.82.0 or later
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Sources:
Reported By: github.com
Extra Source Hub:
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