CVE-2024-30251VulnerabilityPublished 3 Nov 2025

CVE-2024-30251: aio-libs aiohttp · Infinite Loop

Affects aio-libs aiohttpSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 3.9.4 soon.

Data as of 26 Oct 2026, 07:57 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 1.0% chance of exploitation in 30 days – higher than 65% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.9.4

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

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

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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Nov 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 2026-10-26.

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 3.9.4.

Affected software

Product	Affected	Fixed in
PyPIaiohttp`pkg:pypi/aiohttp`Other threats	Affected <3.9.4	Fixed in 3.9.4

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AI-suggested

The primary mitigation is to upgrade all aiohttp deployments to version 3.9.4 or later, where the infinite loop vulnerability has been fixed. For organizations unable to upgrade immediately, applying the official patch or backporting the fix to their current version is critical. Network-level protections such as Web Application Firewalls (WAFs) should be configured to detect and block suspicious multipart/form-data POST requests that could trigger the vulnerability, although crafting precise signatures may be challenging. Rate limiting and anomaly detection on HTTP POST requests can help reduce the risk of exploitation. Monitoring aiohttp server logs for unusual request patterns or repeated multipart/form-data POST requests can provide early warning signs. Additionally, isolating aiohttp services behind reverse proxies or API gateways can add an extra layer of filtering and resilience. Regular security assessments and penetration testing should include attempts to exploit this vulnerability to verify mitigation effectiveness.

Description

### Summary An attacker can send a specially crafted POST (multipart/form-data) request. When the aiohttp server processes it, the server will enter an infinite loop and be unable to process any further requests. ### Impact An attacker can stop the application from serving requests after sending a single request. ------- For anyone needing to patch older versions of aiohttp, the minimum diff needed to resolve the issue is (located in `_read_chunk_from_length()`): ```diff diff --git a/aiohttp/multipart.py b/aiohttp/multipart.py index 227be605c..71fc2654a 100644 --- a/aiohttp/multipart.py +++ b/aiohttp/multipart.py @@ -338,6 +338,8 @@ class BodyPartReader: assert self._length is not None, "Content-Length required for chunked read" chunk_size = min(size, self._length - self._read_bytes) chunk = await self._content.read(chunk_size) + if self._content.at_eof(): + self._at_eof = True return chunk async def _read_chunk_from_stream(self, size: int) -> bytes: ``` This does however introduce some very minor issues with handling form data. So, if possible, it would be recommended to also backport the changes in: https://github.com/aio-libs/aiohttp/commit/cebe526b9c34dc3a3da9140409db63014bc4cf19 https://github.com/aio-libs/aiohttp/commit/7eecdff163ccf029fbb1ddc9de4169d4aaeb6597 https://github.com/aio-libs/aiohttp/commit/f21c6f2ca512a026ce7f0f6c6311f62d6a638866

Impact

For European organizations, this vulnerability poses a significant risk of denial-of-service attacks against web applications and APIs built using vulnerable aiohttp versions. Organizations relying on asynchronous Python frameworks for critical services—such as financial institutions, healthcare providers, government portals, and cloud service providers—may experience service outages or degraded performance if targeted. The attack requires only a single crafted HTTP request, enabling attackers to disrupt services with minimal effort and no authentication. This can lead to operational downtime, loss of customer trust, and potential regulatory repercussions under GDPR if service availability impacts data processing obligations. Additionally, organizations using aiohttp in microservices architectures or as part of larger distributed systems may face cascading failures due to blocked request handling. The lack of known exploits in the wild suggests a window of opportunity for proactive mitigation before widespread exploitation occurs.

Summary

CVE-2024-30251 is a vulnerability classified under CWE-835 (Loop with Unreachable Exit Condition) found in aiohttp, an asynchronous HTTP client/server framework widely used in Python applications for handling HTTP requests asynchronously. The flaw exists in versions prior to 3.9.4, where processing a specially crafted multipart/form-data POST request causes the aiohttp server to enter an infinite loop. This infinite loop prevents the server from processing any further requests, effectively causing a denial-of-service (DoS) condition. The vulnerability requires no privileges or user interaction, making it remotely exploitable over the network by any unauthenticated attacker. The root cause is a logic error in the request parsing code that fails to reach an exit condition under certain malformed input scenarios. The vulnerability was publicly disclosed on May 2, 2024, with a CVSS v3.1 base score of 7.5 (high severity), reflecting its network attack vector, low complexity, no privileges required, and high impact on availability. No known exploits are currently reported in the wild, but the ease of exploitation and impact on availability make it a significant threat. The issue has been addressed in aiohttp version 3.9.4, with users recommended to upgrade or apply manual patches if upgrading is not feasible.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 3 Nov 2025, 22:13 UTC

WeaknessesCWE-835

Technical details

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