Symfony HttpFoundation: Crafted Cache-Control Header Ties Up the CPU

Published as "CVE-2026-108082: ReDoS in HeaderUtils::split() Reachable Through the Cache-Control Request Header"

high Symfony Symfony components · Last reviewed Nov 1, 2026

CVE: CVE-2026-108082
GHSA: GHSA-r925-mgvr-h9cc
Packagist: PKSA-xmwy-rmx5-m7h4
Reported: Sep 15, 2026

Lets an unauthenticated attacker burn close to a second of CPU per request with a crafted Cache-Control header, in any app built on HttpFoundation.

Affected and fixed versions

In 2 packages: symfony/http-foundation and symfony/symfony. Find the row for the version you run, and update to the release next to it.

If you run	Update to	Support
8.1.0 – 8.1.6	8.1.7	Supported
7.4.0 – 7.4.18	7.4.19	Supported
6.4.0 – 6.4.45	6.4.46	Supported
5.4.1 – 5.4.53	5.4.54	Supported

Show 9 older branches, no longer supported

8.0.0 – 8.0.x	8.1.7
7.0.0 – 7.0.x	7.4.19
7.1.0 – 7.1.x	7.4.19
7.2.0 – 7.2.x	7.4.19
7.3.0 – 7.3.x	7.4.19
6.0.1 – 6.0.x	6.4.46
6.1.0 – 6.1.x	6.4.46
6.2.0 – 6.2.x	6.4.46
6.3.0 – 6.3.x	6.4.46

Upgrade

Run the line for the branch you are on. 1 other package listed above is affected too; update it the same way.

composer require symfony/http-foundation:^8.1.7
composer require symfony/http-foundation:^7.4.19
composer require symfony/http-foundation:^6.4.46
composer require symfony/http-foundation:^5.4.54

What this means

An attacker can use up close to a second of CPU with a single request by sending a crafted Cache-Control header. Sent over and over, those requests can slow your app down or stop it from answering. This is a ReDoS: a regular expression that takes far longer on some inputs than on others.

Who is affected

Apps that handle HTTP requests with symfony/http-foundation, also part of symfony/symfony. The Symfony advisory says the header is parsed every time a Request is built, so any app handling HTTP requests is reachable, with no login needed. With longer inputs the parser gives up instead, and every directive in that Cache-Control header is silently dropped.

What to do

Update to 5.4.54, 6.4.46, 7.4.19 or 8.1.7, or later. If you're on 8.0, move to 8.1.

The first release of the fix broke splitting a header on a space in 6.4.46 to 6.4.47, 7.4.19 to 7.4.20 and 8.1.7 to 8.1.8. Versions 6.4.48, 7.4.21 and 8.1.9 fix that as well, so they're the ones to aim for.

Reported by r3verii.

Check your app with an agent

Paste this into a coding agent that can read your project, such as Claude Code, Codex or Amp. It checks your composer.lock against the versions above and tells you what to update, without changing anything.

Check whether the PHP project you have access to is affected by this security advisory, and tell me what to update. Do a read-only check: don't edit files, don't run composer update or composer require, and don't try to reproduce the flaw.

Advisory: Symfony HttpFoundation: Crafted Cache-Control Header Ties Up the CPU (CVE-2026-108082, GHSA-r925-mgvr-h9cc)
Details: https://phpnews.net/security/symfony/ghsa-r925-mgvr-h9cc

Affected versions, as Composer constraints:
- symfony/http-foundation, symfony/symfony: >=5.4.1,<5.4.54|>=6.0.1,<6.1.0|>=6.1.0,<6.2.0|>=6.2.0,<6.3.0|>=6.3.0,<6.4.0|>=6.4.0,<6.4.46|>=7.0.0,<7.1.0|>=7.1.0,<7.2.0|>=7.2.0,<7.3.0|>=7.3.0,<7.4.0|>=7.4.0,<7.4.19|>=8.0.0,<8.1.0|>=8.1.0,<8.1.7

Fixed releases on branches that still get security fixes:
- 8.1.0 – 8.1.6: update to 8.1.7
- 7.4.0 – 7.4.18: update to 7.4.19
- 6.4.0 – 6.4.45: update to 6.4.46
- 5.4.1 – 5.4.53: update to 5.4.54

1. Find every composer.lock in the project outside vendor/ (a monorepo can have one per app) and read the installed version of each package above. Packages installed as dependencies of other packages count too.
2. Compare each installed version with its constraint: "|" separates alternative ranges, and "," means both bounds apply.
3. For each affected install, read "What this means" at https://phpnews.net/security/symfony/ghsa-r925-mgvr-h9cc and check whether the project meets the conditions it describes (a feature in use, a config value, a driver) (if that page won't load, use https://github.com/advisories/GHSA-r925-mgvr-h9cc). Say which conditions you could check and which you couldn't.
4. Report a table: lock file | package | installed version | affected (yes, no or unknown) | conditions met (yes, no or unknown) | update to | evidence. For each affected package, give the command that would fix it, without running it: composer update <package> --with-dependencies when it is only installed as a dependency of another package, or composer require with the fixed version when composer.json requires it directly. If the installed version is on a branch with no fixed release listed, say it needs a move to a newer branch.

Sources

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