VulnerabilityPublished 28 Apr 2026

CVE-2026-40560: MIYAGAWA Starman · HTTP Request/Response Smuggling

Affects MIYAGAWA StarmanSource CVE Database V5

Compare

Not known to be exploited · CVSS 7.5 High : upgrade to 0.4018 soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.4018

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

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

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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Apr 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 30 Oct 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

Upgrade MIYAGAWA Starman to 0.4018.

Affected software

Product	Affected	Fixed in
MIYAGAWAStarman	Affected <0.4018	Fixed in 0.4018
GitHubStarman`pkg:github/Starman`Other threats	Affected <0.4018	Fixed in 0.4018

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, users should consider deploying additional protections at the proxy or firewall level to detect or block suspicious HTTP requests containing conflicting Content-Length and Transfer-Encoding headers. Monitoring for unusual HTTP traffic patterns may help identify attempted exploitation.

Description

CVE-2026-40560 is a high-severity vulnerability in MIYAGAWA Starman versions before 0.4018 for Perl. The issue arises because Starman incorrectly prioritizes the Content-Length header over the Transfer-Encoding: chunked header when both are present in an HTTP request, contrary to RFC 7230 section 3.3.3. This improper header precedence enables HTTP Request Smuggling attacks, where an attacker can send crafted requests that are interpreted inconsistently by front-end reverse proxies and the backend server. There are no known exploits in the wild at this time. The vulnerability affects network-exposed services and has a CVSS score of 7.5, indicating high severity.

Impact

Successful exploitation allows an attacker to perform HTTP Request Smuggling attacks against Starman servers, potentially enabling them to bypass security controls implemented by front-end proxies. This can lead to unauthorized request injection or manipulation. The CVSS score of 7.5 reflects high confidentiality impact but no integrity or availability impact. There are no known active exploits reported.

Summary

Starman versions prior to 0.4018 for Perl contain an HTTP Request Smuggling vulnerability due to improper handling of HTTP headers. Specifically, when both Content-Length and Transfer-Encoding: chunked headers are included in a request, Starman incorrectly gives precedence to Content-Length instead of Transfer-Encoding as mandated by RFC 7230 section 3.3.3. This inconsistency can be exploited by attackers to smuggle malicious HTTP requests through front-end reverse proxies, potentially bypassing security controls or causing unintended behavior in backend services. The vulnerability is tracked as CVE-2026-40560 and is classified under CWE-444 (Inconsistent Interpretation of HTTP Requests).

CWE-444Inconsistent Interpretation of HTTP Requests (HTTP Request Smuggling) (opens in a new tab)
Base weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
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.
Implementation
Use a web server that employs a strict HTTP parsing procedure, such as Apache.
Implementation
Use only SSL communication.
Implementation
Terminate the client session after each request.
OWASP Cheat Sheets
REST Assessment (opens in a new tab)
REST Security (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V13.2.5 (opens in a new tab)
Attack patterns
HTTP Response Smuggling (opens in a new tab)
HTTP Request Smuggling (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 May 2026, 02:11 UTC

WeaknessesCWE-444

Technical details

References

Community reviews

Related threats