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CVE-2026-91991VulnerabilityPublished Updated

livereload · Tornado: Incomplete fix for CVE-2026-35536: cookie attribute injection re-opened via the legacy case-insensitive

Affects livereloadSource GCVE Database

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Mentioned vulnerabilities

Authoritative record:CVE-2026-91991· Medium 6.3

Not known to be exploited · CVSS 6.3 Medium : upgrade to 2.7.1_3 when convenient.

Data as of 30 Oct 2026, 06:45 UTC

CVSS 4.0 base score
6.3Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 2.7.1_3
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 15 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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.

What to do

Upgrade livereload to 2.7.1_3.

Affected software

ProductAffectedFixed in
Homebrewlivereloadpkg:brew/livereloadOther threatsAffected
  • >=2.7.1_1 <2.7.1_3
Fixed in
  • 2.7.1_3

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

AI-suggested

Apply the same validation that rejects control and delimiter characters ([\x00-\x20\x3b\x7f]) to all entries in the **kwargs path after normalizing key case, or remove the deprecated **kwargs path entirely. Ensure regression tests cover capitalized keyword arguments to prevent recurrence. The vulnerability is fixed in Tornado version 2.7.1_3; upgrading to this version or later resolves the issue.

Description

An incomplete fix for CVE-2026-35536 in Tornado's set_cookie method allows cookie attribute injection via capitalized keyword arguments. The original fix validated only lowercase named parameters, but the deprecated **kwargs path accepts capitalized keys without validation, enabling injection of cookie attributes such as Secure, HttpOnly, SameSite, Domain, and Path. This vulnerability affects Tornado versions >=2.7.1_1 and <2.7.1_3 and was fixed in version 2.7.1_3.

References

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