Summary
s2n-quic has excessive memory allocation
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.
Impacted versions: <= v1.81.0
Workarounds
There is no workaround that fully mitigates this issue. Upgrading to the patched version is the recommended remediation.
References
If there are any questions or comments about this advisory, contact AWS Security via the vulnerability reporting page or directly via email to [email protected]. Please do not create a public GitHub issue.
Impact
The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.
CVE-2026-10740 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no 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 (1.82.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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This issue has been addressed in s2n-quic version v1.82.0. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.
Frequently Asked Questions
- What is CVE-2026-10740? CVE-2026-10740 is a medium-severity allocation of resources without limits or throttling vulnerability in s2n-quic (rust), affecting versions <= 1.81.0. It is fixed in 1.82.0. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- How severe is CVE-2026-10740? CVE-2026-10740 has a CVSS score of 5.3 (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.
- Which versions of s2n-quic are affected by CVE-2026-10740? s2n-quic (rust) versions <= 1.81.0 is affected.
- Is there a fix for CVE-2026-10740? Yes. CVE-2026-10740 is fixed in 1.82.0. Upgrade to this version or later.
- Is CVE-2026-10740 exploitable, and should I be worried? Whether CVE-2026-10740 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
- What actually determines whether CVE-2026-10740 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.
- How do I fix CVE-2026-10740? Upgrade
s2n-quicto 1.82.0 or later.