GHSA-r925-mgvr-h9cc CVE-2026-108082
Symfony: ReDoS in HeaderUtils::split() Reachable Through the Cache-Control Request Header
- Severity
- 0.0 / 10
- High · CVSS 4.0
- Exploit chance (EPSS)
- 0.48%
- Chance of exploitation in the next 30 days. Higher than 41.46% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-1333 Inefficient Regular Expression Complexity
- Fix
- Available
- 2 packages have a fixed version
Description
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 for branch 5.4 (and forward-ported to 6.4, 7.4, 8.1 and 8.2).
Credits
Symfony would like to thank r3verii for reporting the issue and Nicolas Grekas for providing the fix.
Symfony would also like to thank Bruno Dias from Checkmarx for his help getting a CVE assigned.
Affected versions
Packagist
| Package | Vulnerable | Fixed in |
|---|---|---|
| symfony/http-foundation | >= 6.0.1, < 6.4.46 |
6.4.46 |
| symfony/http-foundation | >= 7.0.0, < 7.4.19 |
7.4.19 |
| symfony/http-foundation | >= 8.0.0, < 8.1.7 |
8.1.7 |
| symfony/http-foundation | >= 4.1.0, < 5.4.54 |
5.4.54 |
| symfony/symfony | >= 6.0.1, < 6.4.46 |
6.4.46 |
| symfony/symfony | >= 7.0.0, < 7.4.19 |
7.4.19 |
| symfony/symfony | >= 8.0.0, < 8.1.7 |
8.1.7 |
| symfony/symfony | >= 4.1.0, < 5.4.54 |
5.4.54 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
symfony/http-foundation Packagist → 6.4.46
- composer
composer require symfony/http-foundation:^6.4.46
symfony/symfony Packagist → 6.4.46
- composer
composer require symfony/symfony:^6.4.46
Severity breakdown
CVSS 4.0 0.0
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
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- High
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
Weakness
CWE-1333: Inefficient Regular Expression Complexity
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
How to prevent it
- Architecture and Design: Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
- System Configuration: Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
- Implementation: Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
- Implementation: Limit the length of the input that the regular expression will process.
References
Advisories
Packages
Other links
- github.com/symfony/symfony/security/advisories/GHSA-r925-mgvr-h9cc
- github.com/symfony/symfony/pull/66048
- github.com/symfony/symfony/pull/66491
- github.com/symfony/symfony/commit/343a1772ce6ac03e48b228d2d7168d19750e3f36
- github.com/symfony/symfony/commit/9ffa802e5d7e9fb8ba95eeefd27e863e83b1baca
- github.com/FriendsOfPHP/security-advisories/blob/master/symfony/http-foundation…
- github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-202…
- github.com/symfony/symfony/releases/tag/v5.4.54
- github.com/symfony/symfony/releases/tag/v6.4.48
- github.com/symfony/symfony/releases/tag/v7.4.21
- github.com/symfony/symfony/releases/tag/v8.1.9
- symfony.com/blog/cve-2026-108082-redos-in-headerutils-split-reachable-through-th…
- symfony.com/cve-2026-108082
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-2v3c-qxhr-7vpv Symfony: Unbounded Recursion in the YAML Inline Lexer Lets a Single Document Crash the Process | High | Also affects symfony/symfony |
| GHSA-h5x3-xfc9-m39h Symfony: UrlGenerator Dot-Segment Encoding Skips Every Other Chained `../` or `./` → Generated URL Collapses Off-Route Under RFC 3986 Normalization | Medium | Also affects symfony/symfony |
| GHSA-v3wm-qf9p-c549 Symfony: HtmlSanitizer URL Parser Deny Gates Underinclusive: Percent-Encoded BiDi Marks and Unicode Whitespace Bypass Visual-Spoofing Defense | Medium | Also affects symfony/symfony |
| GHSA-rrj9-5q2j-4gvr Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signature Algorithm Downgrade | Medium | Also affects symfony/symfony |
| GHSA-38cx-cq6f-5755 Symfony: IpUtils::PRIVATE_SUBNETS Omits IPv6 Transition Forms (6to4, NAT64, Teredo, IPv4-compatible): SSRF Bypass in NoPrivateNetworkHttpClient | High | Also affects symfony/http-foundation |
| GHSA-6h46-9jf5-q59x Symfony: Security Firewall Bypass via failure_forward Subrequest: Unauthenticated Access to access_control-Protected GET Routes | High | Also affects symfony/symfony |
| GHSA-x5qj-865h-mgvm Symfony: HtmlSanitizer UrlAttributeSanitizer Misses URL Attributes | Medium | Also affects symfony/symfony |
| GHSA-fqc7-9xjw-jrh3 SymfonyRuntime CVE-2024-50340 Patch Bypass: Web Requests Can Still Set APP_ENV/APP_DEBUG via parse_str/SAPI Argv Mismatch | Critical | Also affects symfony/symfony |
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