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CVE-2026-61847— Crass: A large number of adjacent CSS comments can trigger a SystemStackError

Quick assessment

Affected
rgrove crass
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Crass 是一个完全符合 CSS 语法第 3 级规范的 Ruby CSS 解析器。在 1.0.7 版本之前，当未启用 选项（该选项默认未启用）时，Crass 会通过递归读取下一个标记的方式丢弃 CSS 注释。如果攻击者提供的样式表包含大量相邻注释，将导致过度递归并触发 ，从而使解析服务不可用（拒绝服务）。启用注释保留功能可避免进入该递归路径。此问题已在 1.0.7 版本中修复。

CVSS 6.3 · Medium

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
rgrove crass < 1.0.7 affected
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I. Basic Information for CVE-2026-61847

Vulnerability Information
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Vulnerability Title
Crass: A large number of adjacent CSS comments can trigger a SystemStackError
Source: CVE Program / CVE List V5
Vulnerability Description
Crass is a Ruby CSS parser that's fully compliant with the CSS Syntax Level 3 specification. Prior to 1.0.7, when the `:preserve_comments` option is not enabled, which is the default, Crass discards CSS comments by recursively consuming the next token. An attacker-provided stylesheet containing a very large number of adjacent comments can cause excessive recursion and trigger a `SystemStackError`, denying service to the parsing application. Preserving comments avoids this recursive path. This issue is fixed in version 1.0.7.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L
Source: CVE Program / CVE List V5
Vulnerability Type
未经控制的递归
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
rgrove crass < 1.0.7 -

II. Public POCs for CVE-2026-61847

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III. Intelligence Information for CVE-2026-61847

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Other References for CVE-2026-61847 (3)

Same Patch Batch · rgrove · 2026-10-30 · 4 CVEs total

CVE-2026-61845 8.9 HIGH Crass: Large numeric exponents cause CPU and memory denial of service
CVE-2026-61846 6.3 MEDIUM Crass: Deeply nested CSS blocks and functions can trigger a SystemStackError or excessive
CVE-2026-61848 6.3 MEDIUM Crass: Non-ASCII characters cause superlinear CPU consumption

IV. Related Vulnerabilities

Same product: crass
Same vendor: rgrove
Same weakness: CWE-674