high · 8.7 Patched

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

CVE-2026-108082 · GHSA-r925-mgvr-h9cc · published 27 Oct 2026

How serious is it

  • Severity: high, CVSS score 8.7 out of 10.
  • No exploit prediction (EPSS) score yet.
  • Not on the CISA list of exploited vulnerabilities.
  • No public exploit in Exploit-DB.

Is your app affected by CVE-2026-108082?

Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.

Who is affected

  • symfony/http-foundation (Packagist) >= 6.0.1, < 6.4.46
  • symfony/http-foundation (Packagist) >= 7.0.0, < 7.4.19
  • symfony/http-foundation (Packagist) >= 8.0.0, < 8.1.7
  • symfony/symfony (Packagist) >= 6.0.1, < 6.4.46
  • symfony/symfony (Packagist) >= 7.0.0, < 7.4.19
  • symfony/symfony (Packagist) >= 8.0.0, < 8.1.7
  • symfony/http-foundation (Packagist) >= 4.1.0, < 5.4.54
  • symfony/symfony (Packagist) >= 4.1.0, < 5.4.54

How to check

  1. Run composer show symfony/http-foundation in your project to see the installed version, including copies pulled in by other packages.
  2. Run composer show symfony/symfony in your project to see the installed version, including copies pulled in by other packages.
  3. Or paste your lockfile into the checker: it lists every package with a known vulnerability, this one included.

How to fix

Copies a prompt for Claude Code, Cursor or Codex: it checks your lockfiles for this and upgrades it.
  1. On >= 6.0.1, < 6.4.46: Upgrade symfony/http-foundation to 6.4.46 or later, commit the lockfile and redeploy.
  2. On >= 7.0.0, < 7.4.19: Upgrade symfony/http-foundation to 7.4.19 or later, commit the lockfile and redeploy.
  3. On >= 8.0.0, < 8.1.7: Upgrade symfony/http-foundation to 8.1.7 or later, commit the lockfile and redeploy.
  4. On >= 6.0.1, < 6.4.46: Upgrade symfony/symfony to 6.4.46 or later, commit the lockfile and redeploy.
  5. On >= 7.0.0, < 7.4.19: Upgrade symfony/symfony to 7.4.19 or later, commit the lockfile and redeploy.
  6. On >= 8.0.0, < 8.1.7: Upgrade symfony/symfony to 8.1.7 or later, commit the lockfile and redeploy.
  7. On >= 4.1.0, < 5.4.54: Upgrade symfony/http-foundation to 5.4.54 or later, commit the lockfile and redeploy.
  8. On >= 4.1.0, < 5.4.54: Upgrade symfony/symfony to 5.4.54 or later, commit the lockfile and redeploy.
  9. If a vulnerable version was live, check your logs and rotate the secrets that server could read.

The advisory

### 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 given back, and every quantifier is possessive. The first release of this fix broke splitting on a whitespace separator: `HeaderUtils::split('foo bar', ' ')` returned a single value in 6.4.46 to 6.4.47, 7.4.19 to 7.4.20 and 8.1.7 to 8.1.8. Whitespace characters used as separators are now left out of the whitespace branch, which 6.4.48, 7.4.21 and 8.1.9 contain. The patches for this issue are available [here](https://github.com/symfony/symfony/commit/343a1772ce6ac03e48b228d2d7168d19750e3f36) for branch 5.4 (and forward-ported to 6.4, 7.4, 8.1 and 8.2). ### Credits Symfony would like to thank [r3verii](https://github.com/r3verii) for reporting the issue and Nicolas Grekas for providing the fix. Symfony would also like to thank [Bruno Dias](https://github.com/cx-bruno-dias) from Checkmarx for his help getting a CVE assigned.

Check your whole app

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References

Merged from GitHub Advisory Database, OSV. Last updated 28 Oct 2026. All vulnerabilities · RSS · JSON

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