Symfony: HtmlSanitizer allowLinkHosts() / allowMediaHosts() Bypass via URLs Without a Well-Formed Authority (Incomplete Fix for CVE-2026-45066)
Severity and exploitation
KEV coverage does not rule out exploitation.
Assessment vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:NAssessment vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:NSeverity
medium4.3CVSS measures technical severity, not the likelihood of an attack.
Known exploitation
Not listed in the checked CISA KEV catalog
Absence from CISA KEV does not rule out attacks.
Public exploit
Not established by this record
Missing evidence does not mean no public exploit exists.
Remediation
Fix status not established
No structured fix or guidance is available here. Check the latest publisher advisory.
What this means
The Symfony HtmlSanitizer component UrlSanitizer parses URLs differently from browsers, allowing the allowLinkHosts() and allowMediaHosts() checks to be bypassed for URLs without a well-formed authority, resulting in untrusted hosts being referenced in sanitized output in Symfony versions 6.1.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.
Source excerpt · CheckmarxAttack conditions
No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.
Review supporting sources →Affected versions
Check the exact model, release, and any platform requirements against your installation.
sensiolabs · Checkmarx
symfony
3 ranges
sensiolabs · Checkmarx
symfony
Compare with this publisher’s ranges. This does not inspect your installation.
affected
6.1.0 → before 6.4.50
git versions
7.0.0 → before 7.4.23
git versions
8.0.0 → before 8.1.11
git versions
Other versions: unaffected
What to do
Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.
No structured fix or remediation guidance is available here. Check the full source description and vendor’s latest advisory for a patch or workaround; do not assume another version is safe.
cve.new guidance unless attributed to a publisher. This page does not inspect your installation.
Public exploit evidence
No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.
Original source description
Read the full publisher description
The Symfony HtmlSanitizer component UrlSanitizer parses URLs differently from browsers, allowing the allowLinkHosts() and allowMediaHosts() checks to be bypassed for URLs without a well-formed authority, resulting in untrusted hosts being referenced in sanitized output in Symfony versions 6.1.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.
UrlSanitizer parses URLs with league/uri, which follows RFC 3986, while browsers follow the WHATWG URL standard. For URLs without a well-formed authority, such as http:evil.example, ///evil.example, or https://://evil.example/ the sanitizer finds no host, whereas browsers resolve them to evil.example. The guard added for CVE-2026-45066 missed the zero-slash form, and the host 0 was also skipped because PHP treats it as falsy.
This is exploitable when a host allow-list is combined with allowRelativeLinks(true) or allowRelativeMedias(true). The default configuration is not affected.
References
2 sourcesInside the record
Evidence available
Describes the evidence in this view, not whether the product is safe.
Original records
CVE-2026-118517View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.
cve.new JSON →Underlying weaknesses
The source’s classification of what caused the vulnerability.
Environment requirements
These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.
Checkmarx · platform conditions
Any condition may hold
Any condition may hold
Vulnerable product
cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*From (inclusive): 6.1.0
Before: 6.4.50
Vulnerable product
cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*From (inclusive): 7.0.0
Before: 7.4.23
Vulnerable product
cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*From (inclusive): 8.0.0
Before: 8.1.11
Applicability preview
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]Contributing organizations · 2
Assigning organization
Additional data publisher
Timeline
All times UTCAdvisory published
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Source updated
Latest modification date supplied by the source.
Last imported by cve.new
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What changed
Follow changesLarge field values are marked as truncated previews. Original source snapshots remain retained.