CVE-2026-45133

HIGH

7.5

CVSS v3

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, when the parser is exposed to attacker-controlled input, deeply nested mappings or sequences cause both the block-level (Parser::parseBlock()) and inline (Inline::parseSequence() / Inline::parseMapping()) parsers to recurse without a depth limit. A crafted document exhausts the PHP stack and crashes the worker. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.

CWE-674 CWE-776 CWE-1333

How to fix

Remediation Available

symfonyDebian

Fixed in:5.4.53+dfsg-0+deb12u1CVE-2026-45133

Fixed in:6.4.41+dfsg-0+deb13u1CVE-2026-45133

Fixed in:7.4.12+dfsg-1CVE-2026-45133

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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

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploit Intelligence

0.74%probability of exploitation in 30 days

51stpercentile

Moderate risk: more likely to be exploited than 51% of all known CVEs.

References

Patch1

github.com

Release Notes4

Related Vulnerabilities

Other CWE-674 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2021-45105	Medium	5.9	100%	-	Fix
CVE-2024-25111	High	8.6	65%	-	Fix
CVE-2023-50269	High	8.6	58%	-	Fix
CVE-2021-42697	High	7.5	36%	-	Fix
CVE-2018-0739	Medium	6.5	19%	-	Fix
CVE-2007-1285	High	7.5	18%	-	Fix

Common questions

How do I fix CVE-2026-45133?

Upgrade symfony on debian 12 to 5.4.53+dfsg-0+deb12u1 or later.

Is CVE-2026-45133 being actively exploited?

Not that we know of. CVE-2026-45133 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.74% is the estimated probability that it will be exploited in the next 30 days. That is higher than 51% of all scored CVEs.

How severe is CVE-2026-45133?

CVE-2026-45133 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-2026-45133 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.

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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.