CVE-2025-57783VulnerabilityPublished 26 Jan 2026

CVE-2025-57783: Hiawatha Web server · HTTP Request Smuggling

Affects Hiawatha Web serverSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 40% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
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 26 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 2026-10-25.

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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC 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

Affected software

Product	Affected	Fixed in
HiawathaHiawatha Web server	Affected >=11.7 <=8.5	Fixed in–
GitHubhsleisink/hiawatha`pkg:github/hsleisink/hiawatha`Other threats	Affected =11.7	Fixed in–

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

AI-suggested

1. Monitor Hiawatha project communications closely for official patches addressing CVE-2025-57783 and apply updates promptly once available. 2. Until a patch is released, implement strict input validation and HTTP header filtering at the network perimeter or reverse proxy level to detect and block malformed or ambiguous HTTP requests that could be used for request smuggling. 3. Deploy or tune Web Application Firewalls (WAFs) to recognize and mitigate HTTP request smuggling patterns, including anomalies in Content-Length and Transfer-Encoding headers. 4. Conduct thorough security testing, including fuzzing and penetration testing, focusing on HTTP request parsing behavior to identify potential exploitation paths. 5. Segment and isolate critical web server infrastructure to limit lateral movement in case of compromise. 6. Review and harden access control policies on the web server to minimize exposure of sensitive resources. 7. Educate security teams about HTTP request smuggling techniques and signs of exploitation to improve detection and response capabilities. 8. Consider temporary mitigation by disabling or restricting HTTP/1.1 pipelining or keep-alive connections if feasible, as these features can be exploited in request smuggling attacks.

Description

Improper header parsing may lead to request smuggling has been identified in Hiawatha webserver version 11.7 which allows an unauthenticated attacker to access restricted resources managed by Hiawatha webserver.

Impact

For European organizations, the impact of CVE-2025-57783 can be substantial, especially for those relying on Hiawatha Web server version 11.7 to host sensitive web applications or internal services. Unauthorized access to restricted resources can lead to exposure of confidential data, intellectual property theft, or compromise of user credentials. This can result in regulatory non-compliance under GDPR due to data breaches, leading to legal penalties and reputational damage. Additionally, attackers exploiting this vulnerability could manipulate web traffic or perform further attacks such as cross-site scripting or session hijacking, escalating the impact. Critical sectors such as finance, healthcare, government, and critical infrastructure operators using Hiawatha are particularly at risk. The vulnerability's ability to be exploited without authentication increases the attack surface and the likelihood of automated exploitation attempts once details become public. The absence of known exploits currently provides a window for mitigation, but the risk remains high due to the nature of HTTP request smuggling attacks and their potential to bypass traditional security controls like firewalls and WAFs if not properly configured.

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response 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

gitlab.com/hsleisink/hiawatha/-/blame/master/src/http.c?ref_type=heads (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Jan 2026, 18:07 UTC

WeaknessesCWE-444

Technical details

References

Community reviews

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