CVE-2026-126079VulnerabilityPublished 12 Nov 2026Updated 13 Nov 2026

Prior to 8.1.4.1 and 8.0.5.2, with the HTML5 sanitizer (Rails::HTML5::Sanitizer, the default vendor on CRuby for

Affects railsSource GCVE Database

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Authoritative record:CVE-2026-126079· Medium 6.1

Not known to be exploited · CVSS 6.1 Medium.

Data as of 13 Nov 2026, 22:24 UTC

CVSS 3.1 base score

6.1Medium

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	6.1

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Changed
Confidentiality: Low
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: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
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: 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 10 Nov 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 13 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

Affected software

Product	Affected	Fixed in
Ubuntu 26.10rails`pkg:deb/ubuntu/rails?arch=source&distro=stonking`Other threats	Affected =2:7.2.3+dfsg-2 =2:7.2.3.2+dfsg-2	Fixed in–
Ubuntu 26.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=resolute`Other threats	Affected =2:7.2.2.1+dfsg-7 =2:7.2.2.2+dfsg-2 =2:7.2.3+dfsg-2	Fixed in–
Ubuntu 24.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=noble`Other threats	Affected =2:6.1.7.3+dfsg-2build1 =2:6.1.7.3+dfsg-3	Fixed in–
Ubuntu Pro 22.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=esm-apps/jammy`Other threats	Affected =2:6.0.3.7+dfsg-2 =2:6.1.4.1+dfsg-8ubuntu2 =2:6.1.4.1+dfsg-8ubuntu2+esm1	Fixed in–
Ubuntu Pro 20.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=esm-apps/focal`Other threats	Affected =2:5.2.2.1+dfsg-1ubuntu1 =2:5.2.3+dfsg-3 =2:5.2.3+dfsg-3ubuntu0.1~esm1	Fixed in–
Ubuntu Pro 18.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=esm-apps/bionic`Other threats	Affected 2:4.2.9-2 – 2:4.2.10-0ubuntu4+esm2 5 affected builds	Fixed in–

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

AI-suggested

Upgrade Rails to version 8.1.4.1 or 8.0.5.2 or later, where this issue is fixed. Ensure Nokogiri is updated to version 1.19.5 or newer to properly escape < and > characters inside attribute values. Applications using the HTML5 sanitizer with highlight or simple_format helpers should avoid passing untrusted input without these updates.

Description

A vulnerability in the Rails Action View framework prior to versions 8.1.4.1 and 8.0.5.2 affects applications using the default HTML5 sanitizer on CRuby with load_defaults 7.1 or later. Nokogiri versions before 1.19.5 serialize < and > characters unescaped inside attribute values. This can cause the Action View text helpers highlight and simple_format to emit live HTML elements from what should be inert markup, potentially leading to cross-site scripting (XSS) when untrusted input is processed. The issue is fixed in the specified versions.

Impact

This vulnerability allows an attacker to inject malicious HTML elements via untrusted input processed by the highlight or simple_format helpers in Rails applications using the affected sanitizer and Nokogiri versions. This can lead to cross-site scripting (XSS), potentially compromising user sessions or executing arbitrary scripts in the context of the vulnerable web application. The CVSS score is 6.1 (medium severity), reflecting the network attack vector, low complexity, no privileges required, user interaction required, and partial confidentiality and integrity impact.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Nov 2026, 22:24 UTC

Technical details

References

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