CVE-2026-45304
HIGHDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Moderate risk: more likely to be exploited than 53% of all known CVEs.
References
Related Vulnerabilities
Other CWE-776 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2009-1955 | High | 7.5 | 53% | - | Fix |
| CVE-2017-18640 | High | 7.5 | 27% | - | Fix |
| CVE-2019-11253 | High | 7.5 | 26% | - | Fix |
| CVE-2019-12401 | High | 7.5 | 7.4% | - | - |
| CVE-2023-20052 | Medium | 5.3 | 7.0% | - | Fix |
| CVE-2019-15903 | High | 7.5 | 6.6% | - | Fix |
Common questions
How do I fix CVE-2026-45304?
Upgrade symfony on debian 12 to 5.4.53+dfsg-0+deb12u1 or later.
Is CVE-2026-45304 being actively exploited?
Not that we know of. CVE-2026-45304 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.80% is the estimated probability that it will be exploited in the next 30 days. That is higher than 53% of all scored CVEs.
How severe is CVE-2026-45304?
CVE-2026-45304 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-45304 affect?
Published advisories record a fix for symfony (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2026-45304
Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-15.