Symfony: HtmlSanitizer MetaRefreshAttributeSanitizer Matches Only a Narrow Subset of the Browser Refresh Grammar (Incomplete Fix for CVE-2026-48761)
Summary
| CVE | CVE-2026-121373 |
|---|---|
| State | PUBLISHED |
| Assigner | Checkmarx |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-11-04 13:17:27 UTC |
| Updated | 2026-11-04 19:17:30 UTC |
| Description | The Symfony HtmlSanitizer component MetaRefreshAttributeSanitizer, introduced to fix CVE-2026-48761, sanitizes the refresh URL of content attributes of meta tags using a regular expression that is too narrow, allowing sanitization to be bypassed, and resulting in potential URL redirection to untrusted sites 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. The shared declarative refresh steps in the WHATWG HTML Standard require a broader approach: the separator after the time may be ASCII whitespace alone, with no ; or ,, and the url= keyword is optional. Directives the browser honours, but the regular expression misses are returned unchanged, so the attacker URL skips UrlSanitizer entirely and both allowLinkSchemes and allowLinkHosts are defeated for the refresh navigation. This is reachable under any configuration that allows meta with http-equiv and content, including the documented allowStaticElements() preset. |
Risk And Classification
Primary CVSS: v4.0 5.3 MEDIUM from 596c5446-0ce5-4ba2-aa66-48b3b757a647
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Problem Types: CWE-186 | CWE-601 | CWE-186 CWE-186 Overly restrictive regular expression | CWE-601 CWE-601 URL redirection to untrusted site ('open redirect')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 596c5446-0ce5-4ba2-aa66-48b3b757a647 | Secondary | 5.3 | MEDIUM | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/C... |
| 4.0 | CNA | CVSS | 5.3 | MEDIUM | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N |
CVSS v4.0 Breakdown
Attack Vector
NetworkAttack Complexity
LowAttack Requirements
NonePrivileges Required
NoneUser Interaction
PassiveConfidentiality
NoneIntegrity
NoneAvailability
NoneSub Conf.
LowSub Integrity
LowSub Availability
NoneCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Sensiolabs | Symfony | affected 6.1.0 6.4.50 git | Not specified |
| CNA | Sensiolabs | Symfony | affected 7.0.0 7.4.23 git | Not specified |
| CNA | Sensiolabs | Symfony | affected 8.0.0 8.1.11 git | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/symfony/symfony/security/advisories/GHSA-wm2w-4mgj-vw33 | 596c5446-0ce5-4ba2-aa66-48b3b757a647 | github.com | |
| github.com/symfony/symfony/commit/2d4c4fe36200858b91132a95076fff3d9de89d26 | 596c5446-0ce5-4ba2-aa66-48b3b757a647 | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Ilia Alshanetsky (en)
CNA: Nicolas Grekas (en)
There are currently no legacy QID mappings associated with this CVE.