CVE-2026-45304
Symfony: YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs")
Description
Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 5.4.52, 6.4.40, 7.4.12, and 8.0.12, Symfony\Component\Yaml\Parser resolved YAML collection aliases recursively, allowing a small untrusted YAML input to expand into a multi-gigabyte structure and exhaust memory. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.
INFO
Published Date :
July 14, 2026, 7:17 p.m.
Last Modified :
July 14, 2026, 8:25 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-45304
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update Symfony to version 5.4.52 or later.
- Update Symfony to version 6.4.40 or later.
- Update Symfony to version 7.4.12 or later.
- Update Symfony to version 8.0.12 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-45304.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-45304 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-45304
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-45304 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-45304 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 14, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-45304', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-14T19:13:27.727393Z'} -
New CVE Received by [email protected]
Jul. 14, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'symfony', 'product': 'symfony', 'versions': [{'status': 'affected', 'version': '< 5.4.52'}, {'status': 'affected', 'version': '>= 6.0.0-BETA1, < 6.4.40'}, {'status': 'affected', 'version': '>= 7.0.0-BETA1, < 7.4.12'}, {'status': 'affected', 'version': '>= 8.0.0-BETA1, < 8.0.12'}]}, {'vendor': 'symfony', 'product': 'yaml', 'versions': [{'status': 'affected', 'version': '< 5.4.52'}, {'status': 'affected', 'version': '>= 6.0.0-BETA1, < 6.4.40'}, {'status': 'affected', 'version': '>= 7.0.0-BETA1, < 7.4.12'}, {'status': 'affected', 'version': '>= 8.0.0-BETA1, < 8.0.12'}]}] Added Description Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 5.4.52, 6.4.40, 7.4.12, and 8.0.12, Symfony\Component\Yaml\Parser resolved YAML collection aliases recursively, allowing a small untrusted YAML input to expand into a multi-gigabyte structure and exhaust memory. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/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 Added CWE CWE-776 Added Reference https://github.com/symfony/symfony/commit/e77391b2e4f18821198f010d573674c8ed4a970a Added Reference https://github.com/symfony/symfony/releases/tag/v5.4.52 Added Reference https://github.com/symfony/symfony/releases/tag/v6.4.40 Added Reference https://github.com/symfony/symfony/releases/tag/v7.4.12 Added Reference https://github.com/symfony/symfony/releases/tag/v8.0.12 Added Reference https://github.com/symfony/symfony/security/advisories/GHSA-4qpc-3hr4-r2p4