VulnerabilityPublished 21 Apr 2023Updated 21 Nov 2025

CVE-2023-30798: Encode Starlette · Uncontrolled Resource Consumption

Affects Encode StarletteSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 0.25.0 soon.

Data as of 28 Oct 2026, 05:11 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 1.2% chance of exploitation in 30 days – higher than 70% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.25.0

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 21 Apr 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 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 Encode Starlette to 0.25.0.

Affected software

Product	Affected	Fixed in
PyPIstarlette`pkg:pypi/starlette`Other threats	Affected <0.25.0	Fixed in 0.25.0

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

AI-suggested

Upgrade the Starlette framework to version 0.25.0 or later immediately to apply the official fix for this vulnerability.
Implement strict server-side limits on multipart form data processing, including maximum number of parts, maximum size per part, and total request size, to prevent resource exhaustion.
Employ web application firewalls (WAFs) or reverse proxies capable of detecting and blocking abnormal multipart/form-data requests with excessive parts or files.
Monitor HTTP request patterns for spikes in multipart form submissions or unusual request sizes that could indicate exploitation attempts.
Conduct regular dependency audits and vulnerability scans to ensure all components are up to date.
In high-risk environments, consider rate limiting or CAPTCHA challenges on endpoints accepting multipart form data to reduce automated attack feasibility.
Prepare incident response plans to quickly identify and mitigate DoS attacks targeting this vulnerability.
Educate development and operations teams about secure handling of multipart data and resource management best practices.

Description

There MultipartParser usage in Encode's Starlette python framework before versions 0.25.0 allows an unauthenticated and remote attacker to specify any number of form fields or files which can cause excessive memory usage resulting in denial of service of the HTTP service.

Impact

For European organizations, this vulnerability poses a significant risk to the availability of web services built on the Starlette framework. A successful attack can lead to service outages, disrupting business operations, customer access, and critical online services. This is particularly impactful for sectors relying on web applications for real-time data processing, e-commerce, or public services. The denial of service can cause reputational damage and financial losses due to downtime. Since the vulnerability is exploitable without authentication, attackers can launch large-scale or targeted DoS attacks with minimal effort. Organizations with limited incident response capabilities or those that have not updated their dependencies are at higher risk. The impact is magnified in environments where Starlette is used as a core component in microservices or API backends, common in modern European IT infrastructures. Additionally, regulatory compliance frameworks in Europe emphasize service availability, so prolonged outages could have legal and compliance repercussions.

CWE-400Uncontrolled Resource Consumption (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product does not properly control the allocation and maintenance of a limited resource.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place.
Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or; uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
XML Ping of the Death (opens in a new tab)
Regular Expression Exponential Blowup (opens in a new tab)
Sustained Client Engagement (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 21 Nov 2025, 16:29 UTC

WeaknessesCWE-400

Technical details

References

Community reviews

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