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CVE-2026-56858

Fix Javascript regexp context tracking in html/template

MEDIUM
6.1
CVSS Score
Published: August 13, 2026 at 09:58 PM UTC
Updated: September 3, 2026 at 04:54 PM UTC
1 product affected across 1 vendorGo

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Severity
MEDIUM6.1
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

Description

Previously, pathological inputs could close an unescaped '/' early, allowing for attack-controlled data to inject arbitrary content, potentially leading to XSS.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Go· Go Standard Librarygo
60%
v < 1.25.131.26.0-0 ≤ v < 1.26.61.27.0-0 ≤ v < 1.27.0-rc.31.26.0-01.27.0-0
Affected range stops below 1.25.13, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.26.6, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.27.0-rc.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (4)

Source: cverecord
https://go.dev/issue/80435
Source: cverecord
https://go.dev/cl/807100
Source: cverecord
https://groups.google.com/g/golang-announce/c/94pEornpRlI
Source: cverecord
https://pkg.go.dev/vuln/GO-2026-6091

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.1MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-79

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