Immediate
Upgrade Starlet to the vendor-fixed release first and verify production version consistency.
root@hackertop:~/vulnfeed/CVE-2026-40561#
CVE-2026-40561
HIGH
Request Smuggling
✓ Patched◉ PoC 公开◉ Mitigation Active
Lifecycle 5/7
KAZUHO Starlet up to 0.31 on Perl Reverse Proxy Content-Length request smuggling
LIFECYCLE
7.0
CVSS
Vulnerability Description
A vulnerability, which was classified as critical, has been found in KAZUHO Starlet up to 0.31 on Perl. This issue affects an unknown code of the component Reverse Proxy Handler. Applying the patch a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d0 is able to eliminate this problem. The bugfix is ready for download at github.com.
Root Cause Analysis
The manipulation of the argument Content-Length with an unknown input leads to a unknown weakness. Using CWE to declare the problem leads to CWE-444. The product acts as an intermediary HTTP agent
(such as a proxy or firewall) in the data flow between two
entities such as a client and server, but it does not
interpret malformed HTTP requests or responses in ways that
are consistent with how the messages will be processed by
those entities that are at the ultimate destination.
Impact: Impacted is confidentiality, integrity, and availability.
Countermeasure: Applying the patch a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d0 is able to eliminate this problem. The bugfix is ready for download at github.com.
(such as a proxy or firewall) in the data flow between two
entities such as a client and server, but it does not
interpret malformed HTTP requests or responses in ways that
are consistent with how the messages will be processed by
those entities that are at the ultimate destination.
Impact: Impacted is confidentiality, integrity, and availability.
Countermeasure: Applying the patch a7d5dfd1862aafa43e5eaca0fdb6acf4cc15b2d0 is able to eliminate this problem. The bugfix is ready for download at github.com.
Validation (PoC/EXP) - Looking for Contributors
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Mitigation Plan - Sorted by Priority
High
After upgrade, validate configuration and restart services where needed to ensure the fix is active.
High
Use logs and IOCs to hunt through production traffic and confirm whether exploitation traces already exist.
Medium
Keep this issue on the watch list and follow vendor advisories, rollback notices, and new variants.
Vulnerability Lifecycle - Click each stage to inspect details
The issue has entered HackerTop VulnFeed and is now being tracked by the community.
The vulnerability has been synchronized into the platform and entered the visible triage flow.
Initial impact validation is complete based on current disclosure, technical details, and public intelligence.
A public proof path already exists for reference.
No in-the-wild exploitation has been confirmed yet, but monitoring should continue.
The vendor has published a fix. Prioritize upgrade rollout.
Patch and temporary mitigation options are available. Validate deployed versions and IOC coverage.
7.0
CVSS
Temp Score
7.0
HIGH
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Metric Details
Attack Vector
Attack Vector
Network
Attack Complexity
Attack Complexity
Low
Privileges Required
Privileges Required
None
User Interaction
User Interaction
None
Confidentiality Impact
Confidentiality Impact
High
Integrity Impact
Integrity Impact
High
Availability Impact
Availability Impact
High
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CVE-2026-40561 · CVSS 7.0 · Patched
