CVE Catalog

CVE-2026-108082

HighCVSS 8.7
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.37%

29th percentile - higher than 29% of all known CVEs

Summary

In Symfony http-foundation prior to versions 5.4.54, 6.4.46, 7.4.19, and 8.1.7, HeaderUtils::split() parsed header values with a pattern whose token alternative also matched whitespace, followed by a (?<!\s) lookbehind. A run of whitespace before a separator could be divided among iterations in exponentially many ways, causing high CPU usage. HeaderBag calls it for the Cache-Control header whenever a Request is built, so any application handling HTTP requests is reachable without authentication. From 18 spaces on, preg_match_all() gives up at pcre.backtrack_limit and split() returns an empty array, silently dropping every directive of the header.

Risk Assessment

A single request with such a header costs close to a second of CPU, enabling unauthenticated denial of service. Additionally, from 18 spaces on, header directives are silently dropped, which may lead to unexpected application behavior.

Recommendation

Update symfony/http-foundation to version 5.4.54, 6.4.46, 7.4.19, or 8.1.7 (or later). Consider limiting header size and content at the proxy or WAF level.

Related vulnerabilities

Original NVD description (English source)

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to versions 5.4.54, 6.4.46, 7.4.19, and 8.1.7, HeaderUtils::split() parsed header values with a pattern whose token alternative also matched whitespace, followed by a (?<!\s) lookbehind. A run of whitespace placed before a separator could be divided among the iterations of the enclosing repetition in exponentially many ways, and the engine tried all of them before settling. HeaderBag calls it for the Cache-Control header whenever a Request is built, so any application handling HTTP requests is reachable, with no authentication. A single request carrying such a header costs close to a second of CPU (813 ms for a run of 17 spaces in an 8 KB header on PHP 8.5, doubling with each extra space). From 18 spaces on, preg_match_all() gives up at pcre.backtrack_limit and split() returns an empty array, so every directive of the header is silently dropped. This issue affects symfony/http-foundation v4.1.0-BETA1 through v5.4.53, v6.0.0-BETA1 through v6.4.45, v7.0.0-BETA1 through v7.4.18, and v8.0.0-BETA1 through v8.1.6.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS