VulnerabilityPublished 13 Aug 2026Updated 9 Nov 2026

CVE-2026-48817: Starlette · Arbitrary HTTP method dispatched to `HTTPEndpoint` attributes via `getattr`

Affects fastapiSource GCVE Database

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Authoritative record:CVE-2026-48817· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 0.136.3 when convenient.

Data as of 9 Nov 2026, 20:03 UTC

CVSS 3.1 base score

5.3Medium

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

Patch: Available – fixed in 0.136.3

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
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: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on 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 17 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 9 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 fastapi to 0.136.3.

Affected software

Product	Affected	Fixed in
Homebrewfastapi`pkg:brew/fastapi`Other threats	Affected >=0.111.0 <0.136.3	Fixed in 0.136.3

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

AI-suggested

Register HTTPEndpoint subclasses with an explicit methods= argument on the Route, listing only the supported HTTP verbs. This causes the route to reject any other HTTP methods with a 405 Method Not Allowed response before reaching the endpoint, preventing non-standard methods from invoking internal attributes. Additionally, upgrade Starlette to version 0.136.3 or later where this issue is fixed.

Description

Starlette's HTTPEndpoint dispatches HTTP methods by lowercasing the method name and using getattr to call an attribute, without restricting to known HTTP verbs. If a route is registered without an explicit methods= argument, non-standard HTTP methods can invoke internal endpoint attributes not intended as handlers. This can lead to unauthorized invocation of internal methods. FastAPI and other frameworks built on Starlette are also affected. The issue is fixed in Starlette version 0.136.3 by requiring explicit method constraints on routes.

Impact

An attacker can invoke internal methods on HTTPEndpoint subclasses that were never intended to be HTTP handlers by sending requests with crafted non-standard HTTP methods. This can bypass authorization checks applied by intended public handlers, potentially leading to unauthorized actions or information disclosure. The impact is limited to applications that register HTTPEndpoint subclasses without explicit method constraints and define internal methods matching non-standard HTTP method token names.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Nov 2026, 20:03 UTC

Technical details

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