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CVE-2026-45304— Symfony: YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs")

Quick assessment

Affected
symfony symfony
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Symfony是Symfony组织开源的一个用于 Web 和控制台应用程序的 PHP 框架以及一组可重用的 PHP 组件。 Symfony存在资源管理错误漏洞，该漏洞源于YAML解析器递归解析集合别名，可能导致少量不可信YAML输入扩展到多吉字节结构并耗尽内存。以下版本受到影响：5.4.52之前版本、6.4.40之前版本、7.4.12之前版本和8.0.12之前版本。

AI Predicted 7.5 Difficulty: Easy EPSS 0.68% · P51

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 8

VendorProduct Version RangeStatus
symfony symfony < 5.4.52 affected
>= 6.0.0-BETA1, < 6.4.40 affected
>= 7.0.0-BETA1, < 7.4.12 affected
>= 8.0.0-BETA1, < 8.0.12 affected
symfony yaml < 5.4.52 affected
>= 6.0.0-BETA1, < 6.4.40 affected
>= 7.0.0-BETA1, < 7.4.12 affected
>= 8.0.0-BETA1, < 8.0.12 affected
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I. Basic Information for CVE-2026-45304

Vulnerability Information
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Vulnerability Title
Symfony: YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs")
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
DTD中递归实体索引的不恰当限制(XML实体扩展)
Source: CVE Program / CVE List V5
Vulnerability Title
Symfony 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Symfony是Symfony组织开源的一个用于 Web 和控制台应用程序的 PHP 框架以及一组可重用的 PHP 组件。 Symfony存在资源管理错误漏洞，该漏洞源于YAML解析器递归解析集合别名，可能导致少量不可信YAML输入扩展到多吉字节结构并耗尽内存。以下版本受到影响：5.4.52之前版本、6.4.40之前版本、7.4.12之前版本和8.0.12之前版本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
symfony symfony < 5.4.52 -
symfony yaml < 5.4.52 -

II. Public POCs for CVE-2026-45304

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III. Intelligence Information for CVE-2026-45304

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Patches & Fixes for CVE-2026-45304 (3)

Vendor Advisories for CVE-2026-45304 (1)

Vendor Pages for CVE-2026-45304 (1)

Other References for CVE-2026-45304 (1)

Same Patch Batch · symfony · 2026-07-14 · 30 CVEs total

CVE-2026-45133 Symfony: [Yaml] Harden the parser when handling untrusted input
CVE-2026-46644 symfony/polyfill-intl-idn accepts xn-- labels whose Punycode payload decodes to ASCII-only
CVE-2026-48761 Symfony: HtmlSanitizer UrlAttributeSanitizer Misses URL Attributes on <object>, <applet>,
CVE-2026-48736 Symfony: IpUtils::PRIVATE_SUBNETS Omits IPv6 Transition Forms (6to4, NAT64, Teredo, IPv4-c
CVE-2026-48747 Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signatu
CVE-2026-48760 Symfony: HtmlSanitizer URL Parser Deny Gates Underinclusive: Percent-Encoded BiDi Marks an
CVE-2026-48489 Symfony: Security Firewall Bypass via failure_forward Subrequest: Unauthenticated Access t
CVE-2026-48784 Symfony: UrlGenerator Dot-Segment Encoding Skips Every Other Chained `../` or `./` → Gener
CVE-2026-47212 Symfony: Twilio Notifier Webhook Parser Never Verifies the X-Twilio-Signature HMAC: Unauth
CVE-2026-45068 Symfony: Argument Injection in SendmailTransport via Dash-Prefixed Recipient Address
CVE-2026-45071 Symfony: XXE (Local File Disclosure) in DomCrawler::addXmlContent() via validateOnParse =
CVE-2026-47767 Symfony: SymfonyRuntime CVE-2024-50340 Patch Bypass: Web Requests Can Still Set APP_ENV/AP
CVE-2026-45075 Symfony: HEAD Request Bypasses methods: ['GET'] Filter in #[IsGranted] / #[IsSignatureVali
CVE-2026-45063 Symfony: Identity Spoofing via Unanchored DN Regex in X509Authenticator
CVE-2026-45070 Symfony: Email Header Injection via Non-Token Characters in Mime Parameter Names
CVE-2026-45756 Symfony: JsonPath Evaluates Attacker-Controlled Regular Expressions in match()/search() Wi
CVE-2026-45754 Symfony: Mailjet Mailer Webhook Parser Never Verifies the Configured Secret — Unauthentica
CVE-2026-45069 Symfony: OidcTokenHandler Accepts JWTs Missing aud/iss/exp Claims
CVE-2026-45753 Symfony: HtmlSanitizer UrlAttributeSanitizer Omits action/formaction/poster/cite — javascr
CVE-2026-45072 Symfony: Stored XSS in WebProfiler CodeExtension::fileExcerpt() — Unescaped Non-PHP File R

Showing top 20 of 30 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: symfony
Same vendor: symfony
Same weakness: CWE-776

V. Comments for CVE-2026-45304

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