CVE-2026-56858: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in Go standard library html/template
CVE-2026-56858 is a cross-site scripting (XSS) vulnerability in the Go standard library's html/template package. The flaw allows pathological inputs to prematurely close an unescaped '/' character, enabling injection of arbitrary content controlled by an attacker. This improper neutralization of input during web page generation could lead to XSS attacks. The vulnerability affects specific versions of the Go html/template package. No official patch or remediation guidance is currently provided by the vendor. There are no known exploits in the wild at this time.
AI Analysis
Technical Summary
The vulnerability CVE-2026-56858 in the Go standard library html/template package involves improper neutralization of input during web page generation, classified under CWE-79 (Cross-site Scripting). Specifically, certain pathological inputs can close an unescaped '/' character early, allowing attacker-controlled data to inject arbitrary content into generated web pages. This can potentially lead to XSS attacks. The affected versions include exactly 1.26.0-0, 1.27.0-0, all versions before 1.25.13, and versions from 1.26.0-0 up to but not including 1.26.6. There is no CVSS score or official remediation level published yet, and no known exploits have been reported.
Potential Impact
If exploited, this vulnerability could allow an attacker to inject arbitrary content into web pages generated by the html/template package, potentially leading to cross-site scripting attacks. This could result in the execution of malicious scripts in the context of the victim's browser, impacting confidentiality and integrity of user interactions with affected applications. However, no active exploitation has been reported so far.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or remediation level is provided, users should monitor the Go project advisories for updates. Until a fix is available, carefully validate and sanitize inputs before passing them to the html/template package to reduce risk.
CVE-2026-56858: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in Go standard library html/template
Description
CVE-2026-56858 is a cross-site scripting (XSS) vulnerability in the Go standard library's html/template package. The flaw allows pathological inputs to prematurely close an unescaped '/' character, enabling injection of arbitrary content controlled by an attacker. This improper neutralization of input during web page generation could lead to XSS attacks. The vulnerability affects specific versions of the Go html/template package. No official patch or remediation guidance is currently provided by the vendor. There are no known exploits in the wild at this time.
Affected software
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability CVE-2026-56858 in the Go standard library html/template package involves improper neutralization of input during web page generation, classified under CWE-79 (Cross-site Scripting). Specifically, certain pathological inputs can close an unescaped '/' character early, allowing attacker-controlled data to inject arbitrary content into generated web pages. This can potentially lead to XSS attacks. The affected versions include exactly 1.26.0-0, 1.27.0-0, all versions before 1.25.13, and versions from 1.26.0-0 up to but not including 1.26.6. There is no CVSS score or official remediation level published yet, and no known exploits have been reported.
Potential Impact
If exploited, this vulnerability could allow an attacker to inject arbitrary content into web pages generated by the html/template package, potentially leading to cross-site scripting attacks. This could result in the execution of malicious scripts in the context of the victim's browser, impacting confidentiality and integrity of user interactions with affected applications. However, no active exploitation has been reported so far.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or remediation level is provided, users should monitor the Go project advisories for updates. Until a fix is available, carefully validate and sanitize inputs before passing them to the html/template package to reduce risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Go
- Date Reserved
- 2026-06-23T15:10:49.353Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a7e412ebf8831d539e0511f
Added to database: 08/13/2026, 22:11:58 UTC
Last enriched: 08/13/2026, 22:27:53 UTC
Last updated: 08/14/2026, 01:00:26 UTC
Views: 5
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.