VulnerabilityPublished 6 Mar 2026Updated 16 Mar 2026

CVE-2026-27142: Go standard library html/template · Cross-site Scripting

Affects Go standard library html/templateSource CVE Database V5

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Not known to be exploited · CVSS 6.1 Medium : upgrade to 1.26.1 or 1.25.8 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

6.1Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 27% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.26.1, 1.25.8

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 6 Mar 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 30 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 Go standard library html/template to 1.26.1 or 1.25.8.

Affected software

Product	Affected	Fixed in
Go standard libraryhtml/template	Affected >=1.26.0-0 <1.26.1	Fixed in 1.26.1
Go standard libraryhtml/template	Affected <1.25.8	Fixed in 1.25.8
Gohtml/template`pkg:golang/html/template`Other threats	Affected <1.25.8 >=1.26.0-0 <1.26.1	Fixed in 1.25.8 1.26.1
Gogithub.com/golang/go/src/html/template`pkg:golang/github.com/golang/go/src/html/template`Other threats	Affected =0 =1.26.0-0	Fixed in–

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

AI-suggested

The new GODEBUG setting htmlmetacontenturlescape can be used to control escaping behavior, but its use may disable escaping and potentially increase risk if misconfigured. If you cannot patch yet, carefully review and sanitize any user-controlled input that may be inserted into meta refresh content attributes.

Description

CVE-2026-27142 is a medium severity cross-site scripting (XSS) vulnerability in the Go standard library's html/template package. It occurs because URLs inserted into the content attribute of HTML meta tags are not properly escaped when the meta tag includes an http-equiv attribute with the value "refresh". This improper neutralization can allow an attacker to inject malicious scripts. A new GODEBUG setting, htmlmetacontenturlescape, has been introduced to control escaping behavior for URLs in meta content attributes.

Impact

Successful exploitation could allow an attacker to execute arbitrary scripts in the context of the affected web application by injecting malicious content into meta refresh tags. This can lead to partial confidentiality and integrity impacts as indicated by the CVSS vector. There is no indication of availability impact. No known exploits are reported in the wild at this time.

Summary

The vulnerability in Go's html/template package arises from improper escaping of URLs inserted into the content attribute of HTML meta tags that also have an http-equiv="refresh" attribute. This can lead to cross-site scripting (CWE-79) attacks. The issue affects Go versions up to 1.26.0-0. A new environment variable setting, htmlmetacontenturlescape, allows disabling escaping of URLs in these contexts, which may influence mitigation strategies. The CVSS 3.1 base score is 6.1, indicating medium severity, with network attack vector, low attack complexity, no privileges required, user interaction required, scope changed, and low confidentiality and integrity impact.

CWE-79Improper Neutralization of Input During Web Page Generation (Cross-site Scripting) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 3 Jun 2026, 21:22 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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