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Fencer Vulns
medium 5.8

CVE-2026-55767 json

Guzzle: Dot-Only Cookie Domains Match All Hosts in guzzlehttp/guzzle

published 2026-06-19 4 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-38457 , GHSA-cwxw-98qj-8qjx

cvss
5.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

Summary

Guzzle is an extensible PHP HTTP client. Prior to 7.12.1, CookieJar incorrectly accepts cookies with a dot-only Domain attribute and whitespace-padded variants. SetCookie::matchesDomain() removes leading dots from the cookie domain, normalizing dot-only values to the empty string; SetCookie::validate() only rejected a strictly empty domain, so these cookies could be stored and the empty normalized domain was treated as matching any request host. An attacker-controlled origin that an application requests with a shared cookie jar can therefore set a cookie that Guzzle later sends to unrelated hosts using the same jar. This may allow cookie injection or session fixation against downstream services, depending on how those services interpret the injected cookie. This vulnerability is fixed in 7.12.1.

Patch / fix

  • packagist guzzlehttp/guzzle 7.12.1
  • guzzlephp guzzle 7.12.1
  • guzzle Debian 14 7.12.1-1

debian advisories DEBIAN-CVE-2026-55767

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-55767 updated cvss 7.2

guzzlehttp/guzzle: Guzzle: Cookie injection and session fixation due to improper domain validation

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
GitHub 3.1 5.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
packagist guzzlehttp/guzzle
<7.12.1
7.12.1

Affected products

  • guzzle guzzle

Classification

Weakness
  • CWE-346 Origin Validation Error
  • CWE-1286 Improper Validation of Syntactic Correctness of Input

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.