CVE-2026-45066Public exploitNetwork attack vector

Off-allowlist navigation via parsing and policy errors

Published Jul 14, 2026 · Updated Jul 14, 2026

URL allowlist bypass in Symfony HTML Sanitizer allows remote attackers to retain off-list URLs that browsers resolve differently. UrlSanitizer parses backslashes and irregular scheme slashes under RFC 3986 rather than browser WHATWG rules, while UrlAttributeSanitizer routes area href values through the media policy. Exploitation requires an application to sanitize attacker-controlled HTML with link or media allowlists; resulting links can direct users to an unintended host or scheme.

CVSS severity2.3
Low
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

URL allowlist bypass in Symfony HTML Sanitizer allows remote attackers to retain off-list URLs that browsers resolve differently. UrlSanitizer parses backslashes and irregular scheme slashes under RFC 3986 rather than browser WHATWG rules, while UrlAttributeSanitizer routes area href values through the media policy. Exploitation requires an application to sanitize attacker-controlled HTML with link or media allowlists; resulting links can direct users to an unintended host or scheme.

The record

CVE
CVE-2026-45066
Published
Jul 14, 2026
Updated
Jul 14, 2026
Vendor
Symfony
Product
Symfony
Classifications
CWE-436, CWE-184
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 6.1.0-BETA1, < 6.4.40
  2. Affected versionversion=>= 7.0.0-BETA1, < 7.4.12
  3. Affected versionversion=>= 8.0.0-BETA1, < 8.0.12

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Symfony · Symfonyversion=>= 6.1.0-BETA1, < 6.4.40; version=>= 7.0.0-BETA1, < 7.4.12; version=>= 8.0.0-BETA1, < 8.0.12
Symfony · Symfony HTML Sanitizerversion=>= 6.1.0-BETA1, < 6.4.40; version=>= 7.0.0-BETA1, < 7.4.12; version=>= 8.0.0-BETA1, < 8.0.12

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
2.3GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-436Interpretation Conflict
CWE-184Incomplete List of Disallowed Inputs

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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