Report · AWS Security BulletinsAbout CVE-2026-10740Published 10 Jun 2026Updated 19 Oct 2026

CVE-2026-10740: s2n-quic · Excessive Memory Allocation

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Authoritative record:CVE-2026-10740· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium · fixed in 2.246.0 : update s2n-quic when convenient.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Affects: s2n-quic before 1.82.0
Patch: Available – fixed in 2.246.0, 2.245.0

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

AI-suggested

A fix is available in s2n-quic version v1.82.0. Users should upgrade to this version or later to remediate the vulnerability. There are no effective workarounds that fully mitigate this issue.

Description

Bulletin ID: 2026-042-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 06/10/2026 11:15 AM PDT Description: s2n-quic is a Rust implementation of the QUIC protocol. We identified CVE-2026-10740, an issue of unbounded memory allocation in the CRYPTO frame reassembler in s2n-quic before 1.82.0. 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: < v1.82.0 Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.

Impact

An unauthenticated attacker can cause excessive memory allocation on an s2n-quic server by sending crafted CRYPTO frames, potentially leading to denial of service due to memory exhaustion. No authentication or valid handshake is required to exploit this vulnerability.

Summary

The vulnerability CVE-2026-10740 in s2n-quic involves unbounded memory allocation in the CRYPTO frame reassembler. The buffer used to process CRYPTO frames does not enforce a maximum size, allowing an unauthenticated attacker to send crafted CRYPTO frames with high offsets to exhaust server memory. This can cause denial of service without requiring a valid handshake. The issue affects all s2n-quic versions before v1.82.0. The vendor has released version v1.82.0 with a fix that addresses this excessive memory allocation. No workaround fully mitigates the issue, so upgrading is the recommended remediation.

References

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