VulnerabilityPublished 29 Oct 2026

CVE-2026-115927: Tornado · Event loop blocking and excess memory use from chunked bodies with many small chunks

Affects livereloadSource GCVE Database

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Authoritative record:CVE-2026-115927· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium · fixed in 6.6 : update livereload when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score

5.3Medium

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	5.3

EPSS: 0.3% chance of exploitation in 30 days – higher than 32% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 6.6

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

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

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: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 26 Oct 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 29 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.
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

Affected software

Product	Affected	Fixed in
Homebrewlivereload`pkg:brew/livereload`Other threats	Affected >=2.7.1	Fixed in–

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AI-suggested

A fix is available in Tornado version 6.6, which addresses the issue by yielding to the event loop during body processing, combining small chunks, and optimizing memory usage. Applications should upgrade to Tornado 6.6 or later. As a workaround, deploy Tornado behind a reverse proxy that buffers request bodies and forwards them with a Content-Length header instead of chunked encoding. Additionally, lowering the max_body_size setting can reduce the maximum blocking time and memory usage per request but does not fully mitigate the vulnerability.

Description

Tornado HTTP servers are vulnerable to event loop blocking and excessive memory use when processing HTTP/1.1 chunked transfer encoded bodies composed of many small chunks. An attacker can send a request body with millions of 1-byte chunks, causing the server to block the event loop for extended periods and consume significantly more memory than the actual body size. This affects any handler that reads the request body without prior rejection and requires no authentication. The issue also impacts Tornado's SimpleAsyncHTTPClient when reading responses from malicious servers. The vulnerability is fixed in Tornado 6.6.

Impact

The vulnerability allows unauthenticated attackers to cause denial of service by blocking the Tornado event loop for extended periods and causing excessive memory consumption. This impacts availability by delaying or blocking other connections handled by the same process. The SimpleAsyncHTTPClient is also vulnerable when reading responses from malicious servers. Lowering max_body_size reduces but does not eliminate the risk. No confidentiality or integrity impacts are reported.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 29 Oct 2026, 18:52 UTC

Technical details

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