guzzlehttp/psr7: Host Confusion via Weak URI Host Validation

Exploitation

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

CVSS

4.2 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

EPSS

• CVE-2026-59882: 0.32% estimated exploitation activity in the next 30 days; percentile 24.71 (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.

Impact guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVERNAME or SERVERADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of 'gggg:' while getAuthority() returns '[gggg::1'. You are affected if your application builds a Uri or calls Uri::withHost()…

Published by the source

21 Jul 2026, 18:35 UTC

Last modified by the source

21 Jul 2026, 18:35 UTC

Source last checked

26 Oct 2026, 14:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-c2w2-prh8-qm98

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# Patch Next advisory brief: CVE-2026-59882

Advisory: guzzlehttp/psr7: Host Confusion via Weak URI Host Validation
IDs: CVE-2026-59882, GHSA-c2w2-prh8-qm98
Record: https://patchnext.com/advisories/cve-2026-59882 (revision 1, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: guzzlehttp/psr7 2.12.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist guzzlehttp/psr7: affected < 2.12.3; fixed in 2.12.3

## Suggested inspection (read-only)
- Packagist guzzlehttp/psr7: 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 guzzlehttp/psr7.
- 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-c2w2-prh8-qm98 (GitHub-reviewed advisory GHSA-c2w2-prh8-qm98 lists affected ranges: Packagist guzzlehttp/psr7 >=0 <2.12.3)

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