What is CVE-2026-48736?

CVE-2026-48736 is a medium-severity server-side request forgery (SSRF) vulnerability in symfony/http-client (composer), affecting versions >= 5.4.0, < 5.4.53. It is fixed in 5.4.53, 6.4.41, 7.4.13, 8.0.13. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.

Which packages are affected by CVE-2026-48736?

symfony/http-client (composer) versions >= 5.4.0, = 6.4.0, = 5.4.0, < 5.4.53.

Is there a fix for CVE-2026-48736?

Yes. CVE-2026-48736 is fixed in 5.4.53, 6.4.41, 7.4.13, 8.0.13. Upgrade to this version or later.

Is CVE-2026-48736 exploitable, and should I be worried?

Whether CVE-2026-48736 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2026-48736 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

CVE-2026-48736 in symfony/http-client | Intelligent Application Security

Q: Which packages are affected by CVE-2026-48736?

symfony/http-client (composer) versions >= 5.4.0, = 6.4.0, = 5.4.0, < 5.4.53.

Q: Is there a fix for CVE-2026-48736?

Yes. CVE-2026-48736 is fixed in 5.4.53, 6.4.41, 7.4.13, 8.0.13. Upgrade to this version or later.

Q: Is CVE-2026-48736 exploitable, and should I be worried?

Whether CVE-2026-48736 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2026-48736 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2026-48736?

Upgrade: symfony/http-client to 5.4.53 or later, symfony/http-foundation to 6.4.41 or later, symfony/http-foundation to 7.4.13 or later, symfony/http-foundation to 8.0.13 or later, symfony/symfony to 5.4.53 or later, symfony/symfony to 6.4.41 or later, symfony/symfony to 7.4.13 or later, symfony/symfony to 8.0.13 or later.

Summary

Description

Symfony\Component\HttpClient\NoPrivateNetworkHttpClient is documented as a decorator that blocks requests to private networks by default. The list of blocked subnets (Symfony\Component\HttpFoundation\IpUtils::PRIVATE_SUBNETS on 6.4+, a private constant in NoPrivateNetworkHttpClient on 5.4) enumerates RFC1918, loopback, link-local and IPv4-mapped IPv6 (::ffff:0:0/96) prefixes, but omits the remaining IPv6 transition forms that can embed a private IPv4 destination: 6to4 (2002::/16, RFC 3056), Teredo (2001::/32, RFC 4380), NAT64 (64:ff9b::/96, RFC 6052 and 64:ff9b:1::/48, RFC 8215) and IPv4-compatible IPv6 (::/96, RFC 4291 §2.5.5.1).

IpUtils::checkIp6() is a pure bitwise CIDR comparison against the constants list and never extracts the embedded IPv4, so an attacker who can supply a URL writes the loopback / RFC1918 IPv4 target as e.g. http://[2002:7f00:1::]/ (6to4 → 127.0.0.1), http://[64:ff9b::7f00:1]/ (NAT64 → 127.0.0.1), http://[::7f00:1]/ (IPv4-compatible → 127.0.0.1) or http://[2001::1]/ (Teredo). IpUtils::isPrivateIp() returns false and NoPrivateNetworkHttpClient dispatches the request.

Real-world reachability of the embedded IPv4 depends on the deploy's IPv6 routing (6to4 tunnel interface, upstream NAT64 gateway, kernel handling of IPv4-compatible addresses), but the security boundary the decorator promises, the dispatch decision, is crossed regardless of whether the packet ultimately lands on the embedded IPv4.

Resolution

The private-subnet list now includes ::/96, 2002::/16, 2001::/32, 64:ff9b::/96 and 64:ff9b:1::/48. Blanket blocking of these prefixes matches the policy applied by Chromium and Mozilla's Private Network Access; server-side HTTPS APIs are not legitimately published on these prefixes.

The patches for this issue are available here for branch 5.4 and here for branch 6.4 (and forward-ported to 7.4, 8.0 and 8.1).

Credits

Symfony would like to thank tonghuaroot for reporting the issue and Nicolas Grekas for providing the fix.

Impact

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

Affected versions

symfony/http-client (>= 5.4.0, < 5.4.53) symfony/http-foundation (>= 6.4.0, < 6.4.41) symfony/http-foundation (>= 7.0.0, < 7.4.13) symfony/http-foundation (>= 8.0.0, < 8.0.13) symfony/symfony (>= 5.4.0, < 5.4.53) symfony/symfony (>= 6.4.0, < 6.4.41) symfony/symfony (>= 7.0.0, < 7.4.13) symfony/symfony (>= 8.0.0, < 8.0.13)

Security releases

symfony/http-client → 5.4.53 (composer) symfony/http-foundation → 6.4.41 (composer) symfony/http-foundation → 7.4.13 (composer) symfony/http-foundation → 8.0.13 (composer) symfony/symfony → 5.4.53 (composer) symfony/symfony → 6.4.41 (composer) symfony/symfony → 7.4.13 (composer) symfony/symfony → 8.0.13 (composer)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

See it in your environment

Remediation advice

Upgrade the following packages to resolve this vulnerability:

symfony/http-client to 5.4.53 or later; symfony/http-foundation to 6.4.41 or later; symfony/http-foundation to 7.4.13 or later; symfony/http-foundation to 8.0.13 or later; symfony/symfony to 5.4.53 or later; symfony/symfony to 6.4.41 or later; symfony/symfony to 7.4.13 or later; symfony/symfony to 8.0.13 or later

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2026-48736? CVE-2026-48736 is a medium-severity server-side request forgery (SSRF) vulnerability in symfony/http-client (composer), affecting versions >= 5.4.0, < 5.4.53. It is fixed in 5.4.53, 6.4.41, 7.4.13, 8.0.13. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
Which packages are affected by CVE-2026-48736?
- symfony/http-client (composer) (versions >= 5.4.0, < 5.4.53)
- symfony/http-foundation (composer) (versions >= 6.4.0, < 6.4.41)
- symfony/symfony (composer) (versions >= 5.4.0, < 5.4.53)
Is there a fix for CVE-2026-48736? Yes. CVE-2026-48736 is fixed in 5.4.53, 6.4.41, 7.4.13, 8.0.13. Upgrade to this version or later.
Is CVE-2026-48736 exploitable, and should I be worried? Whether CVE-2026-48736 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2026-48736 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2026-48736?
- Upgrade symfony/http-client to 5.4.53 or later
- Upgrade symfony/http-foundation to 6.4.41 or later
- Upgrade symfony/http-foundation to 7.4.13 or later
- Upgrade symfony/http-foundation to 8.0.13 or later
- Upgrade symfony/symfony to 5.4.53 or later
- Upgrade symfony/symfony to 6.4.41 or later
- Upgrade symfony/symfony to 7.4.13 or later
- Upgrade symfony/symfony to 8.0.13 or later

Other vulnerabilities in symfony/http-client

CVE-IDSeverityPackage summary

CVE-2024-50342Lowsymfony/http-client: Symfony allows internal address and port enumeration by NoPrivateNetworkHttpClient