CVE-2026-45305Network attack vector

Service hang via cleanup regex backtracking

Published Jul 14, 2026 · Updated Jul 14, 2026

Regular expression denial of service in Symfony Yaml before 5.4.52, 6.4.40, 7.4.12, or 8.0.12 allows remote attackers to hang parsing. Parser::cleanup() applies overlapping quantifiers to YAML directive, leading-comment, and document-marker text, causing catastrophic backtracking on oversized crafted lines. Any application that passes attacker-controlled YAML to the parser is exposed, and one input can consume CPU for an arbitrarily long time.

CVSS severity8.7
High
EPSS probability0.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Symfony Yaml before 5.4.52, 6.4.40, 7.4.12, or 8.0.12 allows remote attackers to hang parsing. Parser::cleanup() applies overlapping quantifiers to YAML directive, leading-comment, and document-marker text, causing catastrophic backtracking on oversized crafted lines. Any application that passes attacker-controlled YAML to the parser is exposed, and one input can consume CPU for an arbitrarily long time.

The record

CVE
CVE-2026-45305
Published
Jul 14, 2026
Updated
Jul 14, 2026
Vendor
Symfony
Product
Symfony
Classifications
CWE-1333, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 5.4.52
  2. Affected versionversion=>= 6.0.0-BETA1, < 6.4.40
  3. Affected versionversion=>= 7.0.0-BETA1, < 7.4.12
  4. Affected versionversion=>= 8.0.0-BETA1, < 8.0.12

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Symfony · Symfonyversion=< 5.4.52; version=>= 6.0.0-BETA1, < 6.4.40; version=>= 7.0.0-BETA1, < 7.4.12; version=>= 8.0.0-BETA1, < 8.0.12
Symfony · Symfony Yamlversion=< 5.4.52; version=>= 6.0.0-BETA1, < 6.4.40; version=>= 7.0.0-BETA1, < 7.4.12; version=>= 8.0.0-BETA1, < 8.0.12

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7GitHub, Inc.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
2.7GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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