symfony: Incomplete List of Disallowed Inputs
CVE-2026-48736 is a high-severity incomplete list of disallowed inputs vulnerability in symfony, with a CVSS 3.1 base score of 8.6 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected symfony versions: >= 5.4.0, < 5.4.53; >= 6.0.0-BETA1, < 6.4.41; >= 7.0.0-BETA1, < 7.4.13, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.57% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of symfony you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Symfony | symfony | >= 5.4.0, < 5.4.53; >= 6.0.0-BETA1, < 6.4.41; >= 7.0.0-BETA1, < 7.4.13; >= 8.0.0-BETA1, < 8.0.13 | Not stated |
| Symfony | http-client | >= 5.4.0, < 5.4.53 | Not stated |
| Symfony | http-foundation | >= 6.0.0-BETA1, < 6.4.41; >= 7.0.0-BETA1, < 7.4.13; >= 8.0.0-BETA1, < 8.0.13 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 6.9 | Medium | CNA (github.com) |
| CVSS 3.1 | 8.6 | High | NVD |
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Incomplete List of Disallowed Inputs
The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete.
How developers prevent this class of flaw
- Do not rely exclusively on detecting disallowed inputs. There are too many variants to encode a character, especially when different environments are used, so there is a high likelihood of missing some variants. Only use detection of disallowed inputs as a mechanism for detecting suspicious activity. Ensure that you are using other protection mechanisms that only identify good input - such as lists of allowed inputs - and ensure that you are properly encoding your outputs.
More Incomplete List of Disallowed Inputs vulnerabilities (CWE-184)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- github.com/symfony/symfony/commit/82765368cf74177c36613575182f168a2eb765b2
- github.com/symfony/symfony/commit/85b831555be8ea1f43bf01078afe87bc4c92f65e
- github.com/symfony/symfony/releases/tag/v5.4.53Release Notes
- github.com/symfony/symfony/releases/tag/v6.4.41Release Notes
- github.com/symfony/symfony/releases/tag/v7.4.13Release Notes
Other vulnerabilities in symfony
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
- 7.5 High severity
- 7.5 High severity
Recent Incomplete List of Disallowed Inputs vulnerabilities
- 8.8 High severity
- 8.8 High severity
- 8.3 High severity
- 8.8 High severity
- 7.6 High severity
- 8.6 High severity
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