CVE-2026-16756
Allocation of resources without limits in the default aws-smithy-http-server serve() path allows unauthenticated Slowloris denial of service
Missing connection and header-read timeouts and the absence of a concurrent-connection cap in the default serve() path of Amazon aws-smithy-http-server might allow remote attackers to cause a denial of service by opening many connections and sending partial requests that are never completed, exhausting server sockets and tasks.
To mitigate this issue, users should upgrade to aws-smithy-http-server 0.66.5 or later.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Allocation of resources without limits in the default aws-smithy-http-server serve() path allows unauthenticated Slowloris denial of service
Missing connection and header-read timeouts and the absence of a concurrent-connection cap in the default serve() path of Amazon aws-smithy-http-server might allow remote attackers to cause a denial of service by opening many connections and sending partial requests that are never completed, exhausting server sockets and tasks.
To mitigate this issue, users should upgrade to aws-smithy-http-server 0.66.5 or later.
- Record
CVE-2026-16756- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-770
- Updated
- 2026-11-02
EUVDEUVD-2026-48362
Missing connection and header-read timeouts and the absence of a concurrent-connection cap in the default serve() path of Amazon aws-smithy-http-server might allow remote attackers to cause a denial of service by opening many connections and sending partial requests that are never completed, exhausting server sockets and tasks.
To mitigate this issue, users should upgrade to aws-smithy-http-server 0.66.5 or later.
- Record
EUVD-2026-48362- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-jvxp-qmx7-gjpx
Smithy-RS: Allocation of resources without limits in the default aws-smithy-http-server serve() path allows unauthenticated Slowloris denial of service
Summary
Smithy-RS is a Rust code generation and runtime framework that generates HTTP clients and servers from Smithy interface definitions, powering the AWS SDK for Rust and custom service implementations. An issue exists where, under certain circumstances, allocation of resources without limits in the default aws-smithy-http-server serve() path allows unauthenticated Slowloris denial of service.
Impact
Missing connection and header-read timeouts and the absence of a concurrent-connection cap in the default serve() path of Amazon aws-smithy-http-server might allow remote attackers to cause a denial of service by opening many connections and sending partial requests that are never completed, exhausting server sockets and tasks.
Impacted versions: aws-smithy-http-server <= 0.66.4
Patches
This issue has been addressed in aws-smithy-http-server version 0.66.5. AWS recommends upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.
Workarounds
There is no workaround besides updating to the patched version.
Contact
If you have any questions or comments about this advisory, AWS asks that you contact AWS Security via the vulnerability reporting page or directly via email to [email protected]. Please do not create a public GitHub issue.
- Record
GHSA-jvxp-qmx7-gjpx- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-770
- Updated
- 2026-11-02
NVD
Missing connection and header-read timeouts and the absence of a concurrent-connection cap in the default serve() path of Amazon aws-smithy-http-server might allow remote attackers to cause a denial of service by opening many connections and sending partial requests that are never completed, exhausting server sockets and tasks.
To mitigate this issue, users should upgrade to aws-smithy-http-server 0.66.5 or later.
- Record
CVE-2026-16756- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-770
- Updated
- 2026-11-02
OSVGHSA-jvxp-qmx7-gjpx
Smithy-RS: Allocation of resources without limits in the default aws-smithy-http-server serve() path allows unauthenticated Slowloris denial of service
Summary
Smithy-RS is a Rust code generation and runtime framework that generates HTTP clients and servers from Smithy interface definitions, powering the AWS SDK for Rust and custom service implementations. An issue exists where, under certain circumstances, allocation of resources without limits in the default aws-smithy-http-server serve() path allows unauthenticated Slowloris denial of service.
Impact
Missing connection and header-read timeouts and the absence of a concurrent-connection cap in the default serve() path of Amazon aws-smithy-http-server might allow remote attackers to cause a denial of service by opening many connections and sending partial requests that are never completed, exhausting server sockets and tasks.
Impacted versions: aws-smithy-http-server <= 0.66.4
Patches
This issue has been addressed in aws-smithy-http-server version 0.66.5. AWS recommends upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.
Workarounds
There is no workaround besides updating to the patched version.
Contact
If you have any questions or comments about this advisory, AWS asks that you contact AWS Security via the vulnerability reporting page or directly via email to [email protected]. Please do not create a public GitHub issue.
- Record
GHSA-jvxp-qmx7-gjpx- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-770
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
aws-smithy-http-servercrates.io |
through 0.66.4 | 0.66.5 |
aws-smithy-http-servercrates.io |
before 0.66.5 | 0.66.5 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-16756 is a high vulnerability (CVSS 8.7) in Aws Aws-smithy-http-server, published July 23, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.75%, the 55th percentile. Fixed in aws-smithy-http-server 0.66.5.
