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SymfonyFramework / library · Sensiolabs

CVE-2026-48736

HIGH · 8.6 CVSS v3.1 Published 2026-07-14
Fix available
A fix is available. Upgrade to 5.4.43 / 6.4.41 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Symfony is a PHP framework for web and console applications and a set of reusable PHP components. From 5.4.0 to 5.4.53, 6.4.41, 7.4.13, and 8.0.13, NoPrivateNetworkHttpClient and IpUtils::PRIVATE_SUBNETS omitted IPv6 transition prefixes such as 6to4, NAT64, Teredo, and IPv4-compatible IPv6, allowing attacker-supplied URLs to represent private IPv4 targets in forms that IpUtils::isPrivateIp() did not block. This issue is fixed in versions 5.4.53, 6.4.41, 7.4.13, and 8.0.13.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In Symfony versions 5.4.0-5.4.53, 6.4.x before 6.4.41, 7.4.x before 7.4.13, and 8.0.x before 8.0.13, the NoPrivateNetworkHttpClient and IpUtils::PRIVATE_SUBNETS failed to filter IPv6 transition prefixes (6to4, NAT64, Teredo, and IPv4-compatible IPv6). This allowed attacker-controlled URLs to represent private IPv4 targets in ways that IpUtils::isPrivateIp() did not block, bypassing private network access controls.

MitigationUpgrade Symfony to versions 5.4.53, 6.4.41, 7.4.13, 8.0.13 or later to include proper IPv6 transition prefix filtering in the private IP detection logic.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
SymfonyFramework / library
Affected:>= 5.4.0, < 5.4.43>= 6.4.0, < 6.4.41>= 7.0.0, < 7.4.13>= 8.0.0, < 8.0.13

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Symfony version
    Run `composer show symfony/symfony` or check your composer.lock file for the symfony/symfony package version
    Affected if The installed version is >= 5.4.0 and < 5.4.43, or >= 6.4.0 and < 6.4.41, or >= 7.0.0 and < 7.4.13, or >= 8.0.0 and < 8.0.13
  2. Search for IpUtils usage
    Search your codebase for calls to `IpUtils::isPrivateIp()` or references to `IpUtils::PRIVATE_SUBNETS`
    Affected if Your application uses these methods to validate IP addresses against private network ranges
  3. Search for NoPrivateNetworkHttpClient usage
    Search your codebase for uses of `NoPrivateNetworkHttpClient` class or service
    Affected if Your application uses this HTTP client to restrict outgoing requests to public networks
  4. Inspect IpUtils implementation
    Locate the IpUtils.php file in vendor/symfony/security-http/Util/IpUtils.php (or similar path) and examine the isPrivateIp() method for IPv6 transition prefix handling
    Affected if The isPrivateIp() method does not contain filtering for 2002::/16 (6to4), 64:ff9b::/96 (NAT64), 2001::/32 (Teredo), or ::ffff:0:0/96 (IPv4-mapped IPv6) prefixes

You are affected if you run a vulnerable Symfony version AND use IpUtils::isPrivateIp() or NoPrivateNetworkHttpClient to block private network access, and your application processes untrusted URLs that could contain IPv6 transition notation representing private IPv4 addresses.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.4.43 / 6.4.41 / 7.4.13 or later
Fixed in 5.4.436.4.417.4.13
Interim mitigation

Upgrade Symfony to versions 5.4.53, 6.4.41, 7.4.13, 8.0.13 or later to include proper IPv6 transition prefix filtering in the private IP detection logic.

Recommended fix High confidence

Upgrade to Symfony 5.4.53, 6.4.41, 7.4.13, or 8.0.13 as appropriate for your branch

  1. 1. Identify the current Symfony version in your project by checking composer.json or running `composer show symfony/symfony`
  2. 2. Determine which version branch you are on (5.4.x, 6.4.x, 7.0.x, or 8.0.x)
  3. 3. Run `composer require symfony/symfony:^5.4.53 --no-interaction` for 5.4.x branch, or `composer require symfony/symfony:^6.4.41 --no-interaction` for 6.4.x, or `composer require symfony/symfony:^7.4.13 --no-interaction` for 7.x, or `composer require symfony/symfony:^8.0.13 --no-interaction` for 8.x
  4. 4. Run `composer update symfony/symfony --with-all-dependencies` to apply the update
  5. 5. Run your test suite to verify the application functions correctly after the upgrade
  6. 6. Verify the IpUtils::PRIVATE_SUBNETS constant now includes IPv6 transition prefixes (2002::/16 for 6to4, 64:ff9b::/96 for NAT64, 2001::/32 for Teredo, ::ffff:0:0/96 for IPv4-compatible IPv6)
Caveat Minor patch releases typically have no breaking changes; however, review the Symfony CHANGELOG for your version branch to confirm

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Symfony Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-48736 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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