GHSA-72xp-p242-47p9 CVE-2026-45065
Symfony has a UrlGenerator Route-Requirement Bypass via Unanchored Regex Alternation → Off-Site //host URL Injection
- Severity
- 2.3 / 10
- Low · CVSS 4.0
- Exploit chance (EPSS)
- 0.35%
- Chance of exploitation in the next 30 days. Higher than 28.46% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-185 Incorrect Regular Expression
- CWE-601 URL Redirection to Untrusted Site ('Open Redirect')
- Fix
- Available
- 2 packages have a fixed version
Description
Description
Symfony routes can declare a requirements regex per path parameter, e.g. a route /{_locale}/blog with requirements: { _locale: 'en|fr|de' }. The Twig path() / url() helpers (backed by UrlGenerator) validate supplied parameter values against that regex before building the URL.
UrlGenerator constructs the validation pattern as '#^'.$req.'$#', where $req is the raw requirement string. For a requirement expressed as an alternation, e.g. _locale: 'ar|bg|...|vi|...|zh_CN' (very common), ^ and $ anchor only the first and last alternatives, so any middle alternative matches as an unanchored substring. A value like /evil.com satisfies the requirement (because it contains vi), and the generated path becomes //evil.com/...: a protocol-relative URL the browser navigates off-site.
Resolution
The UrlGenerator class now wraps the requirement in a non-capturing group so the ^ and $ anchors apply to the whole alternation.
The patch for this issue is available here for branch 5.4.
Credits
Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.
Affected versions
Packagist
| Package | Vulnerable | Fixed in |
|---|---|---|
| symfony/routing | < 5.4.52 |
5.4.52 |
| symfony/routing | >= 6.0.0, < 6.4.40 |
6.4.40 |
| symfony/routing | >= 7.0.0, < 7.4.12 |
7.4.12 |
| symfony/routing | >= 8.0.0, < 8.0.12 |
8.0.12 |
| symfony/symfony | < 5.4.52 |
5.4.52 |
| symfony/symfony | >= 6.0.0, < 6.4.40 |
6.4.40 |
| symfony/symfony | >= 7.0.0, < 7.4.12 |
7.4.12 |
| symfony/symfony | >= 8.0.0, < 8.0.12 |
8.0.12 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
symfony/routing Packagist → 5.4.52
- composer
composer require symfony/routing:^5.4.52
symfony/symfony Packagist → 5.4.52
- composer
composer require symfony/symfony:^5.4.52
Severity breakdown
CVSS 4.0 2.3
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/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
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- Present
- Privileges required
- None
- User interaction
- Passive
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- Low
- Integrity (subsequent systems)
- Low
- Availability (subsequent systems)
- None
- Exploit maturity
- Not defined
- Scope
- X
CVSS 3.1 6.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Weakness
CWE-185: Incorrect Regular Expression
The product specifies a regular expression in a way that causes data to be improperly matched or compared.
How to prevent it
- Implementation: Regular expressions can become error prone when defining a complex language even for those experienced in writing grammars. Determine if several smaller regular expressions simplify one large regular expression. Also, subject the regular expression to thorough testing techniques such as equivalence partitioning, boundary value analysis, and robustness. After testing and a reasonable confidence level is achieved, a regular expression may not be foolproof. If an exploit is allowed to slip through, then record the exploit and refactor the regular expression.
CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
How to prevent it
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. Use a list of approved URLs or domains to be used for redirection.
- Architecture and Design: Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
- Architecture and Design: When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs. For example, ID 1 could map to "/login.asp" and ID 2 could map to "http://www.example.com/". Features such as the ESAPI AccessReferenceMap [REF-45] provide this capability.
- Architecture and Design: Ensure that no externally-supplied requests are honored by requiring that all redirect requests include a unique nonce generated by the application [REF-483]. Be sure that the nonce is not predictable (CWE-330).
- Architecture and Design, Implementation: Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls. Many open redirect problems occur because the programmer assumed that certain inputs could not be modified, such as cookies and hidden form fields.
- Operation: Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].
References
Packages
Other links
- github.com/symfony/symfony/security/advisories/GHSA-72xp-p242-47p9
- github.com/symfony/symfony/commit/bcf487c22f3240ba994124e0e0fe8616f3cfc47a
- github.com/FriendsOfPHP/security-advisories/blob/master/symfony/routing/CVE-202…
- github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-202…
- symfony.com/cve-2026-45065
- github.com/symfony/symfony/releases/tag/v5.4.52
- github.com/symfony/symfony/releases/tag/v6.4.40
- github.com/symfony/symfony/releases/tag/v7.4.12
- github.com/symfony/symfony/releases/tag/v8.0.12
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-2v3c-qxhr-7vpv Symfony: Unbounded Recursion in the YAML Inline Lexer Lets a Single Document Crash the Process | High | Also affects symfony/symfony |
| GHSA-r925-mgvr-h9cc Symfony: ReDoS in HeaderUtils::split() Reachable Through the Cache-Control Request Header | High | Also affects symfony/symfony |
| GHSA-h5x3-xfc9-m39h Symfony: UrlGenerator Dot-Segment Encoding Skips Every Other Chained `../` or `./` → Generated URL Collapses Off-Route Under RFC 3986 Normalization | Medium | Also affects symfony/routing |
| GHSA-v3wm-qf9p-c549 Symfony: HtmlSanitizer URL Parser Deny Gates Underinclusive: Percent-Encoded BiDi Marks and Unicode Whitespace Bypass Visual-Spoofing Defense | Medium | Also affects symfony/symfony |
| GHSA-rrj9-5q2j-4gvr Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signature Algorithm Downgrade | Medium | Also affects symfony/symfony |
| GHSA-38cx-cq6f-5755 Symfony: IpUtils::PRIVATE_SUBNETS Omits IPv6 Transition Forms (6to4, NAT64, Teredo, IPv4-compatible): SSRF Bypass in NoPrivateNetworkHttpClient | High | Also affects symfony/symfony |
| GHSA-6h46-9jf5-q59x Symfony: Security Firewall Bypass via failure_forward Subrequest: Unauthenticated Access to access_control-Protected GET Routes | High | Also affects symfony/symfony |
| GHSA-x5qj-865h-mgvm Symfony: HtmlSanitizer UrlAttributeSanitizer Misses URL Attributes | Medium | Also affects symfony/symfony |
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