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The html/template package did not apply the proper rules for handling occurances
of "<script", "<!--", and "</script" within JS literals in <script> contexts.
This may cause the template parser to improperly consider script contexts to be
terminated early, causing actions to be improperly escaped. This could be
leveraged to perform an XSS attack.
Thanks to Takeshi Kaneko (GMO Cybersecurity by Ierae, Inc.) for reporting this
issue.
…ithin the script context
The HTML specification has incredibly complex rules for how to handle
"<!--", "<script", and "</script" when they appear within literals in
the script context. Rather than attempting to apply these restrictions
(which require a significantly more complex state machine) we apply
the workaround suggested in section 4.12.1.3 of the HTML specification [1].
More precisely, when "<!--", "<script", and "</script" appear within
literals (strings and regular expressions, ignoring comments since we
already elide their content) we replace the "<" with "\x3C". This avoids
the unintuitive behavior that using these tags within literals can cause,
by simply preventing the rendered content from triggering it. This may
break some correct usages of these tags, but on balance is more likely
to prevent XSS attacks where users are unknowingly either closing or not
closing the script blocks where they think they are.
Thanks to Takeshi Kaneko (GMO Cybersecurity by Ierae, Inc.) for
reporting this issue.
Fixes#62197Fixes#62398
Fixes CVE-2023-39319
[1] https://html.spec.whatwg.org/#restrictions-for-contents-of-script-elements
Change-Id: Iab57b0532694827e3eddf57a7497ba1fab1746dc
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1976594
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Tatiana Bradley <tatianabradley@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Run-TryBot: Roland Shoemaker <bracewell@google.com>
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/2014619
Reviewed-on: https://go-review.googlesource.com/c/go/+/526097
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
cherrymui
changed the title
security: fix CVE-2023-39319 [1.21 backport]
html/template: improper handling of special tags within script contexts (CVE-2023-39319) [1.21 backport]
Sep 6, 2023
The html/template package did not apply the proper rules for handling occurances
of "<script", "<!--", and "</script" within JS literals in <script> contexts.
This may cause the template parser to improperly consider script contexts to be
terminated early, causing actions to be improperly escaped. This could be
leveraged to perform an XSS attack.
Thanks to Takeshi Kaneko (GMO Cybersecurity by Ierae, Inc.) for reporting this
issue.
This is CVE-2023-39319 and Go issue https://go.dev/issue/62197.
@rolandshoemaker requested issue #62197 to be considered for backport to the next 1.21 minor release.
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