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cvelistGoCVELIST:CVE-2023-24538
HistoryApr 06, 2023 - 3:50 p.m.

CVE-2023-24538 Backticks not treated as string delimiters in html/template

2023-04-0615:50:48
Go
www.cve.org
13
templates
javascript
go
security
escape
injection
error code
godebug flag
backticks

AI Score

9.7

Confidence

High

EPSS

0.007

Percentile

79.9%

Templates do not properly consider backticks (`) as Javascript string delimiters, and do not escape them as expected. Backticks are used, since ES6, for JS template literals. If a template contains a Go template action within a Javascript template literal, the contents of the action can be used to terminate the literal, injecting arbitrary Javascript code into the Go template. As ES6 template literals are rather complex, and themselves can do string interpolation, the decision was made to simply disallow Go template actions from being used inside of them (e.g. “var a = {{.}}”), since there is no obviously safe way to allow this behavior. This takes the same approach as github.com/google/safehtml. With fix, Template.Parse returns an Error when it encounters templates like this, with an ErrorCode of value 12. This ErrorCode is currently unexported, but will be exported in the release of Go 1.21. Users who rely on the previous behavior can re-enable it using the GODEBUG flag jstmpllitinterp=1, with the caveat that backticks will now be escaped. This should be used with caution.

CNA Affected

[
  {
    "vendor": "Go standard library",
    "product": "html/template",
    "collectionURL": "https://pkg.go.dev",
    "packageName": "html/template",
    "versions": [
      {
        "version": "0",
        "lessThan": "1.19.8",
        "status": "affected",
        "versionType": "semver"
      },
      {
        "version": "1.20.0-0",
        "lessThan": "1.20.3",
        "status": "affected",
        "versionType": "semver"
      }
    ],
    "programRoutines": [
      {
        "name": "tJS"
      },
      {
        "name": "tJSDelimited"
      },
      {
        "name": "Template.Execute"
      },
      {
        "name": "Template.ExecuteTemplate"
      }
    ],
    "defaultStatus": "unaffected"
  }
]