VulnerabilityPublished 14 Nov 2023Updated 3 Nov 2025

CVE-2023-47641: aio-libs aiohttp · HTTP Request/Response Smuggling

Affects aio-libs aiohttpSource CVE Database V5

Not known to be exploited · CVSS 3.4 Low : upgrade to 3.8.0 when convenient.

Data as of 26 Oct 2026, 09:15 UTC

CVSS 3.1 base score

3.4Low

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

EPSS: 0.8% chance of exploitation in 30 days – higher than 57% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.8.0

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: Required
Scope: Changed
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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
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: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
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 14 Nov 2023
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

Upgrade aio-libs aiohttp to 3.8.0.

Affected software

Product	Affected	Fixed in
PyPIaiohttp`pkg:pypi/aiohttp`Other threats	Affected <3.8.0	Fixed in 3.8.0

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AI-suggested

The primary mitigation is to upgrade all aiohttp instances to version 3.8.0 or later, where the vulnerability has been fixed. Since no known workarounds exist, patching is critical. Organizations should audit their infrastructure to identify aiohttp usage, particularly in backend services behind reverse proxies that accept both Content-Length and Transfer-Encoding headers. Configuration hardening of reverse proxies to reject or normalize requests containing both headers can reduce risk. Implement strict input validation and header sanitization at the proxy level to prevent malformed TE headers. Monitoring and logging HTTP request anomalies can help detect attempts to exploit request smuggling. Additionally, review and remediate any open redirect vulnerabilities that could be chained with this issue. Employing Web Application Firewalls (WAFs) with updated signatures to detect request smuggling attempts may provide additional protection. Finally, conduct security testing, including fuzzing and penetration testing, focusing on HTTP header parsing inconsistencies in the affected environments.

Description

aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. Affected versions of aiohttp have a security vulnerability regarding the inconsistent interpretation of the http protocol. HTTP/1.1 is a persistent protocol, if both Content-Length(CL) and Transfer-Encoding(TE) header values are present it can lead to incorrect interpretation of two entities that parse the HTTP and we can poison other sockets with this incorrect interpretation. A possible Proof-of-Concept (POC) would be a configuration with a reverse proxy(frontend) that accepts both CL and TE headers and aiohttp as backend. As aiohttp parses anything with chunked, we can pass a chunked123 as TE, the frontend entity will ignore this header and will parse Content-Length. The impact of this vulnerability is that it is possible to bypass any proxy rule, poisoning sockets to other users like passing Authentication Headers, also if it is present an Open Redirect an attacker could combine it to redirect random users to another website and log the request. This vulnerability has been addressed in release 3.8.0 of aiohttp. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Impact

For European organizations, the primary impact of CVE-2023-47641 lies in the potential bypass of proxy security controls and the poisoning of backend connections in aiohttp-based services. This can lead to unauthorized header injection, such as authentication tokens, potentially allowing attackers to impersonate users or escalate privileges within internal applications. Additionally, when combined with open redirect vulnerabilities, attackers could redirect users to malicious websites and capture sensitive request data, impacting user privacy and confidentiality. The vulnerability does not directly affect data integrity or availability but compromises confidentiality in specific deployment scenarios involving reverse proxies and aiohttp backends. Organizations relying on aiohttp for asynchronous HTTP services, especially those exposing APIs or web services behind reverse proxies, are at risk. The lack of known exploits reduces immediate threat but does not eliminate the risk of future attacks. Given the widespread use of Python and aiohttp in web applications and microservices across Europe, especially in sectors like finance, healthcare, and government, exploitation could lead to data leakage and unauthorized access, undermining trust and compliance with data protection regulations such as GDPR.

Summary

CVE-2023-47641 is a vulnerability classified under CWE-444 (Inconsistent Interpretation of HTTP Requests), commonly known as HTTP Request/Response Smuggling, affecting aiohttp, an asynchronous HTTP client/server framework for Python's asyncio. The flaw occurs when both Content-Length (CL) and Transfer-Encoding (TE) headers are present in an HTTP/1.1 request. According to HTTP/1.1 specifications, if both headers exist, the Transfer-Encoding header should take precedence. However, inconsistent parsing between a frontend reverse proxy and the aiohttp backend can lead to different interpretations of the request body length. Specifically, if the frontend proxy ignores a malformed TE header (e.g., 'chunked123') and processes the CL header, while aiohttp backend treats the request as chunked due to the presence of any TE header, this mismatch allows an attacker to smuggle requests. This can poison the backend connection, enabling the attacker to bypass proxy security rules, inject malicious headers such as authentication tokens, or manipulate subsequent requests. If combined with an open redirect vulnerability, attackers could redirect users to malicious sites and log their requests. The vulnerability requires no prior authentication but does require user interaction to send crafted HTTP requests. The issue was addressed in aiohttp version 3.8.0 by correcting the header parsing logic to align with HTTP standards. There are no known workarounds, and no exploits have been observed in the wild as of the publication date (November 14, 2023). The CVSS v3.1 base score is 3.4 (low), reflecting the limited impact and higher complexity due to required conditions and user interaction.

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

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 3 Nov 2025, 22:07 UTC

WeaknessesCWE-444

Technical details

References

Community reviews

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