SensioLabs Symfony up to 5.4.55/6.4.49/7.4.22/8.1.10 Inline/Parser denial of service

Summaryinfo

A vulnerability, which was classified as problematic, has been found in SensioLabs Symfony up to 5.4.55/6.4.49/7.4.22/8.1.10. Affected by this issue is some unknown functionality of the component Inline/Parser. This manipulation causes denial of service. This vulnerability is handled as CVE-2026-123792. The attack can be initiated remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in SensioLabs Symfony up to 5.4.55/6.4.49/7.4.22/8.1.10. It has been declared as problematic. Affected by this vulnerability is an unknown functionality of the component Inline/Parser. The manipulation with an unknown input leads to a denial of service vulnerability. The CWE definition for the vulnerability is CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. As an impact it is known to affect availability. The summary by CVE is:

The Symfony Yaml components Inline and Parser, parse some YAML documents inefficiently, so that a small crafted document can take disproportionately long to process, keeping a PHP process busy for seconds or minutes, potentially causing a denial of service in Symfony versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11. The parser repeats work it has already done in several places. An embedded mapping in a flow sequence is parsed again for every scalar appended to it, and so are the collections nested in it, so the parse time grows exponentially with the nesting depth. The patterns matching mapping keys and tags scan a run of spaces once per character of the run, and each scalar of a flow collection is matched against a copy of the rest of the collection, so the parse time grows quadratically with the size of the input. Nested blocks are also copied at each nesting level, which consumes memory as well as time. A few other constructs, such as an empty sequence item followed by a blank line or an anchor named 0, trigger similar repeated work. Any code parsing untrusted YAML is affected, with the default flags. In Symfony 7.4 and later, that includes #[MapRequestPayload] when the Yaml component is installed and the endpoint does not restrict acceptFormat. A single unauthenticated request with a YAML content type keeps a PHP worker busy until max_execution_time. JSON documents are valid YAML, so a JSON payload sent with a YAML content type is enough for the flow collection case. In Symfony 6.4, #[MapRequestPayload] accepts YAML only when the application registers a yaml request format.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-123792 since 11/06/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 5.4.56, 6.4.50, 7.4.23 or 8.1.11 eliminates this vulnerability.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Programming Tool Software

Vendor

• SensioLabs

Name

• Symfony

Version

• 5.4.0
• 5.4.1
• 5.4.2
• 5.4.3
• 5.4.4
• 5.4.5
• 5.4.6
• 5.4.7
• 5.4.8
• 5.4.9
• 5.4.10
• 5.4.11
• 5.4.12
• 5.4.13
• 5.4.14
• 5.4.15
• 5.4.16
• 5.4.17
• 5.4.18
• 5.4.19
• 5.4.20
• 5.4.21
• 5.4.22
• 5.4.23
• 5.4.24
• 5.4.25
• 5.4.26
• 5.4.27
• 5.4.28
• 5.4.29
• 5.4.30
• 5.4.31
• 5.4.32
• 5.4.33
• 5.4.34
• 5.4.35
• 5.4.36
• 5.4.37
• 5.4.38
• 5.4.39
• 5.4.40
• 5.4.41
• 5.4.42
• 5.4.43
• 5.4.44
• 5.4.45
• 5.4.46
• 5.4.47
• 5.4.48
• 5.4.49
• 5.4.50
• 5.4.51
• 5.4.52
• 5.4.53
• 5.4.54
• 5.4.55
• 6.4.0
• 6.4.1
• 6.4.2
• 6.4.3
• 6.4.4
• 6.4.5
• 6.4.6
• 6.4.7
• 6.4.8
• 6.4.9
• 6.4.10
• 6.4.11
• 6.4.12
• 6.4.13
• 6.4.14
• 6.4.15
• 6.4.16
• 6.4.17
• 6.4.18
• 6.4.19
• 6.4.20
• 6.4.21
• 6.4.22
• 6.4.23
• 6.4.24
• 6.4.25
• 6.4.26
• 6.4.27
• 6.4.28
• 6.4.29
• 6.4.30
• 6.4.31
• 6.4.32
• 6.4.33
• 6.4.34
• 6.4.35
• 6.4.36
• 6.4.37
• 6.4.38
• 6.4.39
• 6.4.40
• 6.4.41
• 6.4.42
• 6.4.43
• 6.4.44
• 6.4.45
• 6.4.46
• 6.4.47
• 6.4.48
• 6.4.49
• 7.4.0
• 7.4.1
• 7.4.2
• 7.4.3
• 7.4.4
• 7.4.5
• 7.4.6
• 7.4.7
• 7.4.8
• 7.4.9
• 7.4.10
• 7.4.11
• 7.4.12
• 7.4.13
• 7.4.14
• 7.4.15
• 7.4.16
• 7.4.17
• 7.4.18
• 7.4.19
• 7.4.20
• 7.4.21
• 7.4.22
• 8.1.0
• 8.1.1
• 8.1.2
• 8.1.3
• 8.1.4
• 8.1.5
• 8.1.6
• 8.1.7
• 8.1.8
• 8.1.9
• 8.1.10

License

• open-source

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CPE 2.2info

• 🔒
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