CVE-2023-24538 Backticks not treated as string delimiters in html/template
Attackers can inject arbitrary JavaScript into Go templates by exploiting improper handling of backticks in JavaScript template literals.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-24538?
CVE-2023-24538 is a critical cross-site scripting vulnerability in Golang Go, published on 6 Apr 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-94
Which versions are affected by CVE-2023-24538?
2 open source packages ship an affected version, including golang and stdlib. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
golang Bitnami | All versions | 1.19.8, 1.20.3 |
stdlib Go | All versions | 1.19.8, 1.20.3 |
Products include Golang Go.
How do I fix CVE-2023-24538?
Upgrade golang to a fixed version for your release line: 1.19.8 or 1.20.3.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2023-24538 being exploited?
There is no known exploitation of CVE-2023-24538 in the wild and no public exploit code.
Public exploit code: 2 proofs of concept on GitHub.
Other vulnerabilities in Golang Go
- CVE-2020-0601 Microsoft Windows CryptoAPI Spoofing
- CVE-2026-27143 Missing bound checks can lead to memory corruption in safe Go in cmd/compile
- CVE-2024-24790 Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip
- CVE-2023-39320 Arbitrary code execution via go.mod toolchain directive in cmd/go
- CVE-2023-24540 Improper handling of JavaScript whitespace in html/template
Sources
Also known as AZL-25992, AZL-25993, AZL-34751, AZL-37296, AZL-37411, AZL-78990 and 10 more.