CVE-2026-108082 Symfony: ReDoS in HeaderUtils::split() Reachable Through the Cache-Control Request Header
Attackers can cause excessive CPU consumption and service unavailability by sending crafted Cache-Control headers to applications using the Symfony HTTP Foundation component.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-108082?
CVE-2026-108082 is a high-severity denial of service vulnerability in sensiolabs symfony, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-1333
Which versions are affected by CVE-2026-108082?
16 open source packages ship an affected version, including symfony/http-foundation and symfony/symfony.
| Package | Affected | Fixed in |
|---|---|---|
symfony/http-foundation Packagist | From 4.1.0 | 5.4.54 |
symfony/http-foundation Packagist | From 4.1.0 | 5.4.54 |
symfony/http-foundation Packagist | From 6.0.1 | 6.4.46 |
symfony/http-foundation Packagist | From 6.0.1 | 6.4.46 |
symfony/http-foundation Packagist | From 7.0.0 | 7.4.19 |
symfony/http-foundation Packagist | From 7.0.0 | 7.4.19 |
10 more packages
symfony/http-foundation Packagist | From 8.0.0 | 8.1.7 |
symfony/http-foundation Packagist | From 8.0.0 | 8.1.7 |
symfony/symfony Packagist | From 4.1.0 | 5.4.54 |
symfony/symfony Packagist | From 4.1.0 | 5.4.54 |
symfony/symfony Packagist | From 6.0.1 | 6.4.46 |
symfony/symfony Packagist | From 6.0.1 | 6.4.46 |
symfony/symfony Packagist | From 7.0.0 | 7.4.19 |
symfony/symfony Packagist | From 7.0.0 | 7.4.19 |
symfony/symfony Packagist | From 8.0.0 | 8.1.7 |
symfony/symfony Packagist | From 8.0.0 | 8.1.7 |
How do I fix CVE-2026-108082?
Upgrade symfony/http-foundation to a fixed version for your release line: 5.4.54, 6.4.46, 7.4.19 or 8.1.7.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-108082 being exploited?
There is no known exploitation of CVE-2026-108082 in the wild and no public exploit code.
Sources
Also known as CLSA-2026-1792529052, CLSA-2026-1792567291, CLSA-2026-1792567795, CLSA-2026-1792567918, DEBIAN-CVE-2026-108082, GHSA-r925-mgvr-h9cc and 1 more.