Symfony: ReDoS in HeaderUtils::split() Reachable Through the Cache-Control Request Header

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · 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 · score source

EPSS

• CVE-2026-108082: 0.48% estimated exploitation activity in the next 30 days; percentile 41.49 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Description `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.

Resolution The pattern now consumes whitespace only when more of the value follows it, so a value can no longer end on whitespace, nothing has to be…

Published by the source

27 Oct 2026, 19:01 UTC

Last modified by the source

27 Oct 2026, 19:15 UTC

Source last checked

28 Oct 2026, 06:30 UTC

1. Revision 2 · amended · 28 Oct 2026

   Amended from osv record GHSA-r925-mgvr-h9cc

2. Revision 1 · created · 27 Oct 2026

   Published from ghsa record GHSA-r925-mgvr-h9cc

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# Patch Next advisory brief: CVE-2026-108082

Advisory: Symfony: ReDoS in HeaderUtils::split() Reachable Through the Cache-Control Request Header
IDs: CVE-2026-108082, GHSA-r925-mgvr-h9cc
Record: https://patchnext.com/advisories/cve-2026-108082 (revision 2, source checked 28 Oct 2026, 06:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: symfony/symfony 8.1.7, 7.4.19, 6.4.46, 5.4.54; symfony/http-foundation 8.1.7, 7.4.19, 6.4.46, 5.4.54. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist symfony/symfony: affected >= 6.0.1, < 6.4.46; >= 7.0.0, < 7.4.19; >= 8.0.0, < 8.1.7; >= 4.1.0, < 5.4.54; fixed in 6.4.46, 7.4.19, 5.4.54, 8.1.7
- Packagist symfony/http-foundation: affected >= 6.0.1, < 6.4.46; >= 7.0.0, < 7.4.19; >= 8.0.0, < 8.1.7; >= 4.1.0, < 5.4.54; fixed in 6.4.46, 7.4.19, 5.4.54, 8.1.7

## Suggested inspection (read-only)
- Packagist symfony/symfony: check the installed version with your package manager.
- Packagist symfony/http-foundation: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on symfony/symfony, symfony/http-foundation.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-r925-mgvr-h9cc (GitHub-reviewed advisory GHSA-r925-mgvr-h9cc lists affected ranges: Packagist symfony/http-foundation >=6.0.1 =7.0.0 =8.0.0 =4.1.0 =6.0.1 =7.0.0 =8.0.0 =4.1.0 <5.4.54)
- Verified: https://osv.dev/vulnerability/GHSA-r925-mgvr-h9cc (OSV record GHSA-r925-mgvr-h9cc lists affected ranges: Packagist symfony/http-foundation >=6.0.1 =7.0.0 =8.0.0 =4.1.0 =6.0.1 =7.0.0 =8.0.0 =4.1.0 <5.4.54 (fixed))

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