VulnerabilityPublished 13 Aug 2026Updated 29 Oct 2026

CVE-2026-49854: Livereload · Tornado has out-of-bounds memory access via C extension

Affects livereloadSource GCVE Database

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Authoritative record:CVE-2026-49854· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 2.7.1_2 when convenient.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.7.1_2

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
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: 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: 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 Jul 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

Upgrade livereload to 2.7.1_2.

Affected software

Product	Affected	Fixed in
Homebrewlivereload`pkg:brew/livereload`Other threats	Affected >=2.7.1 <2.7.1_2	Fixed in 2.7.1_2

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

AI-suggested

Upgrade Tornado to version 2.7.1_2 or later, where this vulnerability is fixed. Until the upgrade can be applied, disable the vulnerable native extension by setting the environment variable TORNADO_EXTENSION=0. This disables the vulnerable code path but may reduce websocket performance.

Description

Tornado's native extension tornado.speedups contains a vulnerability where the websocket_mask function reads four bytes from a mask argument without verifying its length, leading to out-of-bounds memory access. This flaw can expose up to 3 bytes of uninitialized memory. The issue is reachable via Tornado's XSRF token decoder when xsrf_cookies is enabled and the native extension is active. A fix is available in Tornado version 2.7.1_2. Until upgrading, disabling the native extension by setting TORNADO_EXTENSION=0 mitigates the risk at the cost of reduced websocket performance.

Impact

The vulnerability allows an attacker to cause out-of-bounds memory reads, potentially exposing up to three bytes of uninitialized memory. The CVSS score of 3.7 (low severity) reflects limited confidentiality impact with no integrity or availability effects. There are no known exploits in the wild. The flaw affects Tornado's websocket masking implementation when the native extension is enabled and xsrf_cookies is set to true.

Summary

The vulnerability in Tornado's optional native extension tornado.speedups arises because the C function websocket_mask reads four bytes from the mask argument without validating that the mask is exactly four bytes long. When a shorter byte string is passed from Python, this results in reading beyond the buffer boundary, exposing up to three bytes of uninitialized memory. This can be triggered through Tornado's XSRF token decoder if xsrf_cookies is enabled and the native extension is active. The issue is fixed in Tornado version 2.7.1_2. Prior to upgrading, disabling the native extension via the environment variable TORNADO_EXTENSION=0 prevents exploitation.

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Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 06:45 UTC

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