Advisory details:
github_osv / GHSA-r925-mgvr-h9cc
| Advisory ID | github_osv/GHSA-r925-mgvr-h9cc |
| Aliases |
CVE-2026-108082
|
| Summary | Symfony: ReDoS in HeaderUtils::split() Reachable Through the Cache-Control Request Header ### 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. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 7.8 |
| Risk | 3.9 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv4 | 8.7 | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-r925-mgvr-h9cc/GHSA-r925-mgvr-h9cc.json |
| generic_textual | HIGH |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Attack Requirements (AT) | Privileges Required (PR) | User Interaction (UI) | Vulnerable System Impact Confidentiality (VC) | Vulnerable System Impact Integrity (VI) | Vulnerable System Impact Availability (VA) | Subsequent System Impact Confidentiality (SC) | Subsequent System Impact Integrity (SI) | Subsequent System Impact Availability (SA) |
|---|---|---|---|---|---|---|---|---|---|---|
network adjacent local physical |
low high |
none present |
none low high |
none passive active |
high low none |
high low none |
high low none |
high low none |
high low none |
high low none |
There are no SSVC decisions available.