Is CVE-2026-55767 actively exploited?

No active exploitation of CVE-2026-55767 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-55767 be exploited remotely?

Yes. CVE-2026-55767 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-55767?

CVE-2026-55767 has a CVSS score of 5.8 (MEDIUM).

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MEDIUM

CVE-2026-55767

CWE-346Published: June 23, 2026· Updated: Jun 26, 2026

5.8

CVSS v3.1

EPSS:0.11%probability of exploitation in 30 daysPercentile:1.6th

Official Description

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.

NVD Source

Technical Analysis

CVE-2026-55767 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.