CVE-2026-59883: Guzzle CookieJar cross-host cookie disclosure via IP domain matching

CVE-2026-59883 · Severity: medium · CVSS 4.7 · Published 2026-07-08

Guzzle, a popular PHP library for making web requests, contains a flaw in how it handles security cookies for websites identified by IP addresses. An attacker could potentially trick the library into sending sensitive session cookies to the wrong server or inject malicious cookies into a user's session. This could lead to unauthorized access to user accounts or data exposure, particularly in private or development network environments.

Technologies: Guzzle, guzzlehttp/guzzle (Packagist). Vendors: Guzzle, Packagist.

Quick answers

Is CVE-2026-59883 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-59883 being exploited in the wild.
How severe is CVE-2026-59883?
Medium severity, with a CVSS score of 4.7, published 8 July 2026.
Which products and versions are affected?
Guzzle < 7.12.3; guzzlehttp/guzzle (Packagist) < 7.12.3, ECOSYSTEM:introduced=0,fixed=7.12.3.
Is there a fix for CVE-2026-59883?
Yes. guzzlehttp/guzzle (Packagist): upgrade to 7.12.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-59883 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-59883?
Check whether you run Guzzle or guzzlehttp/guzzle (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • guzzlehttp/guzzle (Packagist): upgrade to 7.12.3 or later
    composer require guzzlehttp/guzzle:^7.12.3

Technical details

A vulnerability exists in Guzzle's CookieJar where SetCookie::matchesDomain() incorrectly applies subdomain suffix matching to IP address literals (IPv4, bracketed IPv6, or bare numeric values). Instead of requiring an exact host match as mandated by RFC 6265, Guzzle may send a cookie scoped to an IP like '192.168.0.1' to a look-alike host such as 'evil.192.168.0.1'. Exploitation requires the attacker to have influence over name resolution (e.g., split-horizon DNS or container networks) to resolve the look-alike host. This can result in cookie disclosure, injection, or session fixation. The issue is resolved in version 7.12.3 by enforcing exact matches for IP-based cookie domains.

Affected products

  • GuzzleHTTP guzzle < 7.12.3

Identifiers

  • CVE-2026-59883
  • GHSA-g446-98w2-8p5w

Timeline

  • 2026-06-23: disclosed
  • 2026-07-08: advisory: NVD publication date
  • 2026-07-20: patched: GitHub Advisory reviewed and updated

References

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