Summary
Package updates are available for Amazon Linux 2023 that fix the following vulnerabilities: CVE-2026-42506: Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering. CVE-2026-42504: Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU. CVE-2026-42502: Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering. CVE-2026-39821: The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com") incorrectly returns the name "example.com" rather than an error. This behavior can lead to privilege escalation in programs using the idna package. For example, a program which performs privilege checks on the ASCII hostname may reject "example.com" but permit "xn--example-.com". If that program subsequently converts the ASCII hostname to Unicode, it will inadvertently permits access to the Unicode name "example.com". CVE-2026-27136: Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering. CVE-2026-25681: Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering. CVE-2026-25680: Parsing arbitrary HTML can consume excessive CPU time, possibly leading to denial of service.
Fixed packages 1
| Release | Package | Fixed in |
|---|---|---|
| Amazon Linux · 2023 | runfinch-finch | 0:1.17.1-1.amzn2023.0.3 |
Vulnerabilities 7
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Critical 9.6
Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna
The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com") incorrectly returns the name "example.com" rather than an error. This behavior can lead to privilege …
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High 7.5
Quadratic complexity in WordDecoder.DecodeHeader in mime
Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.
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Medium 6.5
Invoking denial of service when parsing arbitrary HTML in golang.org/x/net/html
Parsing arbitrary HTML can consume excessive CPU time, possibly leading to denial of service.
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Medium 6.1
Invoking incorrect handling of character references in DOCTYPE nodes in golang.org/x/net/html
Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering.
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Medium 6.1
Invoking duplicate attributes can cause XSS in golang.org/x/net/html
Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering.
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Medium 6.1
Invoking incorrect handling of HTML elements in foreign content in golang.org/x/net/html
Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering.
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Medium 6.1
Invoking incorrect handling of namespaced elements in foreign content in golang.org/x/net/html
Parsing arbitrary HTML which is then rendered using Render can result in an unexpected HTML tree. This can be leveraged to execute XSS attacks in applications that attempt to sanitize input HTML before rendering.
References
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web
https://alas.aws.amazon.com/cve/html/CVE-2026-25680.html
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web
https://alas.aws.amazon.com/cve/html/CVE-2026-25681.html
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web
https://alas.aws.amazon.com/cve/html/CVE-2026-27136.html
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web
https://alas.aws.amazon.com/cve/html/CVE-2026-39821.html
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web
https://alas.aws.amazon.com/cve/html/CVE-2026-42502.html
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web
https://alas.aws.amazon.com/cve/html/CVE-2026-42504.html
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web
https://alas.aws.amazon.com/cve/html/CVE-2026-42506.html