VulnerabilityPublished 20 Mar 2025Updated 15 Oct 2025

CVE-2024-6827: benoitc/gunicorn · Inconsistent Interpretation of HTTP Requests

Affects benoitc/gunicornSource CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 3.0 base score

7.5High

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

EPSS: 0.8% chance of exploitation in 30 days – higher than 56% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.0/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 20 Mar 2025
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 26 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.
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
PyPIgunicorn`pkg:pypi/gunicorn`Other threats	Affected =21.2.0	Fixed in–

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AI-suggested

Immediate mitigation should focus on upgrading Gunicorn to a version that properly validates the 'Transfer-Encoding' header and eliminates the fallback to 'Content-Length' parsing. Until a patch is available, organizations should implement strict input validation and filtering at the perimeter, such as configuring web application firewalls (WAFs) to detect and block malformed or suspicious 'Transfer-Encoding' headers. Reverse proxies like Nginx or Apache should be configured to reject ambiguous or conflicting HTTP headers. Network segmentation can limit the impact of SSRF and lateral movement. Monitoring and logging HTTP request anomalies can help detect exploitation attempts early. Additionally, reviewing and hardening caching mechanisms to prevent poisoning and ensuring secure session management practices will reduce risk. Organizations should also conduct penetration testing focused on HTTP request smuggling to identify vulnerable endpoints. Finally, maintaining an incident response plan tailored to web application attacks will improve readiness.

Description

Gunicorn version 21.2.0 does not properly validate the value of the 'Transfer-Encoding' header as specified in the RFC standards, which leads to the default fallback method of 'Content-Length,' making it vulnerable to TE.CL request smuggling. This vulnerability can lead to cache poisoning, data exposure, session manipulation, SSRF, XSS, DoS, data integrity compromise, security bypass, information leakage, and business logic abuse.

Impact

For European organizations, the impact of CVE-2024-6827 can be substantial. Many enterprises and public sector entities in Europe use Gunicorn as part of their web application stacks, especially those leveraging Python frameworks like Django or Flask. Exploitation could lead to unauthorized data disclosure, undermining GDPR compliance and resulting in legal and financial penalties. Cache poisoning and session manipulation could degrade user trust and service integrity, impacting customer-facing applications and internal portals. SSRF and XSS attacks could facilitate lateral movement within networks or compromise end-user devices. Denial of service conditions could disrupt critical services, affecting business continuity. The vulnerability’s remote exploitability without authentication means attackers can target exposed web servers directly, increasing the attack surface. Given Europe's strong regulatory environment and emphasis on data protection, the consequences of a breach exploiting this vulnerability could be severe, including reputational damage and regulatory fines.

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

huntr.com/bounties/1b4f8f38-39da-44b6-9f98-f618639d0dd7 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 15 Oct 2025, 13:34 UTC

WeaknessesCWE-444

Technical details

References

Community reviews

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