CVE-2026-59883Network attack vector

Cookie disclosure and injection via suffix matching

Published Jul 8, 2026 · Updated Jul 8, 2026

Origin validation error in Guzzle before 7.12.3 allows remote attackers to disclose or inject cookies through crafted hostnames. CookieJar stores IP-address and bare-numeric Domain cookies as suffix-matchable, while SetCookie::matchesDomain() checks only the request host for an IP address and therefore sends those cookies to look-alike hosts. Exploitation requires shared cookie support across trust boundaries, a matching IP-scoped cookie, influence over name resolution, and an application request to the look-alike host; impact is limited to cross-host cookie disclosure, injection, or session fixation.

CVSS severity4.7
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Origin validation error in Guzzle before 7.12.3 allows remote attackers to disclose or inject cookies through crafted hostnames. CookieJar stores IP-address and bare-numeric Domain cookies as suffix-matchable, while SetCookie::matchesDomain() checks only the request host for an IP address and therefore sends those cookies to look-alike hosts. Exploitation requires shared cookie support across trust boundaries, a matching IP-scoped cookie, influence over name resolution, and an application request to the look-alike host; impact is limited to cross-host cookie disclosure, injection, or session fixation.

The record

CVE
CVE-2026-59883
Published
Jul 8, 2026
Updated
Jul 8, 2026
Vendor
Guzzle
Product
Guzzle
Classifications
CWE-200, CWE-346, CWE-384, T1539
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 7.12.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Guzzle · Guzzleversion=< 7.12.3

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.7GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
CWE-346Origin Validation Error
CWE-384Session Fixation
T1539Steal Web Session Cookie

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo