CVE
Loofah CSS sanitization bypass in url() filtering
- Exploited
- No known exploitation
- Fix
- Fixed in 2.25.3
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 2.25.3.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- FIRST's estimate of the chance attackers exploit it in the next 30 days, updated daily.What do these mean? →
- 0.29% · 21st percentile
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 22/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Loofah, a general library for manipulating and transforming HTML and XML documents, has a CSS sanitization flaw that lets crafted style content bypass its url() checks. Remotely, without logging in, an attacker can make a viewer's browser request an attacker-chosen URL when the content renders or is hovered over, which can reveal the viewer's IP address, user agent, and access timing, and reach internal-network hosts, though no script survives and the attacker cannot read the response.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. Prior to 2.25.3, Loofah::HTML5::Scrub.scrub_css checks only the first parse of a style attribute, then rebuilds CSS with identifier escapes decoded so escaped parentheses, property names, comments, or quotes can become a live url() without a second safety check. An attacker can use list-style to make a viewer's browser request an attacker-chosen URL when content renders, or cursor to make the request on hover. The request can disclose the viewer's IP address, user agent, access timing, and access to internal-network hosts, but no script survives sanitization and the attacker cannot read the response. This issue is fixed in version 2.25.3.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure7/25Reachable over the network without a login · Unknown: No advisory context yet
- Reach10/20Affects RubyGems packages
- Severity4.7/10CVSS 4.7
- No patch0/5No signal
What would change the score
- Would score about 77 if added to CISA KEV
- Would score about 72 if CISA's SSVC rates exploitation active
- Would score about 37 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 2.25.3.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-126207 (Loofah: CSS url() sanitization bypass via escaped parentheses), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-126207 (entry last updated 2026-11-12):
Affected:
- flavorjones loofah: fixed in 2.25.3
- RubyGems package loofah: fixed in 2.25.3
Fixed versions: 2.25.3.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-126207 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126207 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Packages (RubyGems): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/flavorjones/loofah/security/advisories/GHSA-m3x9-938q-5767
- https://github.com/flavorjones/loofah/pull/324
- https://github.com/flavorjones/loofah/commit/b198a36e44c9c5408163ac50787825e8ca0b166b
- https://github.com/flavorjones/loofah/releases/tag/v2.25.3
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-126207
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126207"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- flavorjones loofah
fixed in 2.25.3
- loofahRubyGems
fixed in 2.25.3
Evidence 6
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Other links · 3
- Repository
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-126207
Is CVE-2026-126207 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-126207?
loofah: before 2.25.3. loofah (RubyGems): before 2.25.3.Source: cve.now feed data
How do I fix CVE-2026-126207?
Upgrade to a fixed version: 2.25.3.Source: cve.now feed data