How severe is CVE-2026-108082?

No CVSS score has been assigned to CVE-2026-108082 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-108082?

CVE-2026-108082 affects the following packages: symfony/http-foundation (Packagist), symfony/http-foundation (Packagist), symfony/http-foundation (Packagist), symfony/symfony (Packagist), symfony/symfony (Packagist), symfony/symfony (Packagist), symfony/http-foundation (Packagist), symfony/symfony (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-108082?

Update symfony/http-foundation to 6.4.46 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-108082 is resolved across your whole dependency graph.

How do I detect CVE-2026-108082 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/http-foundation, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-108082 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-108082 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-108082 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-108082?

CVE-2026-108082 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 41th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-108082?

CVE-2026-108082 is classified as CWE-1333 (CWE-1333). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-108082 published, and has it been updated?

CVE-2026-108082 was published on October 15, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2026-108082 — http-foundation

Fix: symfony/symfony#66048

CVE-2026-108082 is a CWE-1333 vulnerability in symfony/http-foundation. A fix is available for symfony/http-foundation — see the affected versions and patch details below.

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

Also known asGHSA-r925-mgvr-h9cc

Published

Oct 15, 2026

Updated

Oct 28, 2026

Affected

8 pkgs

Patched

8 / 8

Exploits

None indexed

Exploitation data as of Oct 27, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-108082.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs41th percentile — riskier than 41% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

8 pkgs affected

🐘symfony/http-foundation🐘symfony/http-foundation🐘symfony/http-foundation🐘symfony/symfony🐘symfony/symfony🐘symfony/symfony🐘symfony/http-foundation🐘symfony/symfony

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

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 Packages

8 total 8 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`symfony/http-foundation`	≥ 6.0.1&&< 6.4.46	6.4.46`composer require symfony/http-foundation:^6.4.46`
🐘Packagist	`symfony/http-foundation`	≥ 7.0.0&&< 7.4.19	7.4.19`composer require symfony/http-foundation:^7.4.19`
🐘Packagist	`symfony/http-foundation`	≥ 8.0.0&&< 8.1.7	8.1.7`composer require symfony/http-foundation:^8.1.7`
🐘Packagist	`symfony/symfony`	≥ 6.0.1&&< 6.4.46	6.4.46`composer require symfony/symfony:^6.4.46`
🐘Packagist	`symfony/symfony`	≥ 7.0.0&&< 7.4.19	7.4.19`composer require symfony/symfony:^7.4.19`
🐘Packagist	`symfony/symfony`	≥ 8.0.0&&< 8.1.7	8.1.7`composer require symfony/symfony:^8.1.7`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/http-foundation, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update symfony/http-foundation to 6.4.46 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-108082 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### 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

O3 Security · Impact-Aware SCA

Is CVE-2026-108082 in your dependencies?

Find it across Packagist, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVE-2026-108082 — http-foundation

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

Real-World Exposure

Description

Description

Resolution

Credits

Affected Packages

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2026-108082 in your dependencies?