Memory exhaustion via recursive collection-alias expansion
Published Jul 14, 2026 · Updated Jul 14, 2026
Denial of service in Symfony Yaml allows remote attackers to exhaust memory by submitting crafted YAML with recursive collection aliases. Symfony\Component\Yaml\Parser resolves aliases to arrays, stdClass objects, and TaggedValue-wrapped collections without limiting shared recursive expansion. Any application that parses attacker-controlled YAML can expand a small document into a multi-gigabyte structure and terminate its PHP worker.
Summary
What happened
Denial of service in Symfony Yaml allows remote attackers to exhaust memory by submitting crafted YAML with recursive collection aliases. Symfony\Component\Yaml\Parser resolves aliases to arrays, stdClass objects, and TaggedValue-wrapped collections without limiting shared recursive expansion. Any application that parses attacker-controlled YAML can expand a small document into a multi-gigabyte structure and terminate its PHP worker.
The record
- CVE
- CVE-2026-45304
- Published
- Jul 14, 2026
- Updated
- Jul 14, 2026
- Vendor
- Symfony
- Product
- Symfony
- Classifications
- CWE-776, CAPEC-197, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 14, 2026CVE publishedPublication date reported by the CVE source.
- Jul 14, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 5.4.52
- Affected versionversion=>= 6.0.0-BETA1, < 6.4.40
- Affected versionversion=>= 7.0.0-BETA1, < 7.4.12
- Affected versionversion=>= 8.0.0-BETA1, < 8.0.12
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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