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Advisory severityMedium4.7Red Hat Linux

Medium [CVE-2026-59883] Cross-host cookie disclosure and injection due to improper domain matching in CookieJar.

This medium-severity Red Hat Linux advisory covers CVE-2026-59883.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.

CVE-2026-59883 Source published Source updated

VulniPulse record published

CVE-2026-59883
Affected products & platforms
Red Hat LinuxUnclassified
Open source advisory

Summary

Guzzle is an extensible PHP HTTP client.

Prior to 7.12.3, CookieJar did not restrict cookies scoped to IP-address or bare-numeric Domain values to the exact host that set them, because SetCookie::matchesDomain() applied ordinary suffix matching to domains such as 192.168.0.1, [::1], or 1, allowing cross-host cookie disclosure, cookie injection, or session fixation.

This issue is fixed in version 7.12.3. This vulnerability could allow a remote attacker to disclose cookies across different hosts, inject malicious cookies, or fixate user sessions, potentially leading to unauthorized access or session hijacking.

Red Hat's products are not affected by this flaw because the guzzlehttp/guzzle PHP library is not shipped in any Red Hat product. Red Hat severity: Moderate — CVSS 4.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N).

Weakness: CWE-472.

Is CVE-2026-59883 exploited?

No exploitation is reported in the sources VulniPulse tracks: CVE-2026-59883 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.

How do I fix CVE-2026-59883?

Upgrade to a fixed release named by Red Hat:

  • 7.12.3

Confirm against the vendor advisory before you patch.

Affected versions
  • < 7.12.3
  • < 192.168.0.1

Official advisory · high-confidence parse· fetched 23 hours ago·verify at source

Fixed versions
  • 7.12.3

Official advisory · high-confidence parse· fetched 23 hours ago·verify at source

Mitigation checklist

Recommended fix / mitigation
  • Use a separate CookieJar instance per host or trust boundary. Do not store cookies scoped to IP-address or bare-numeric domains in a shared jar.

Official advisory · high-confidence parse· fetched 23 hours ago·verify at source

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