CVE-2026-69245 in Guzzle
Summary
by MITRE • 08/04/2026
Guzzle is an extensible PHP HTTP client. Prior to 7.15.2 and 8.0.1, SetCookie::matchesDomain() gives every subdomain of a cookie Domain that cookie unless SetCookie::matchesDomain() recognizes the Domain as an IP literal or a numeric host, and the decision comes from the domain's own text, so two spellings a transport reads as an address keep subdomain scope. Hexadecimal and mixed-base forms such as 0x7f000001 and 0177.0.0.0x1 go unrecognized while libcurl 8.21.0 reads both as 127.0.0.1. A percent-escaped Domain keeps that scope on both branches because percent-decoding sits above numeric parsing, so 192.168.0.%31 and 127.0.0.1%2e are registered names in the URI grammar rather than address literals, and no numeric rule in any base classifies them, while libcurl decodes the host before resolving and reads them as 192.168.0.1 and 127.0.0.1. A cookie stored for Domain=0x7f000001 is placed in the Cookie header of a request to evil.0x7f000001, disclosing a session identifier or token to a host that is not that address, and a response from evil.0x7f000001 setting Domain=0x7f000001 is accepted into the jar and replayed to the address, so a server answering for the look-alike name can fix a session or set application state. Exploitation requires the application to enable cookie support, address an origin by one of these spellings, and contact a host whose name ends in that spelling. This issue is fixed in versions 7.15.2 and 8.0.1.
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Analysis
by VulDB Data Team • 08/04/2026
The vulnerability in Guzzle's SetCookie::matchesDomain() function represents a critical domain matching flaw that enables cross-domain cookie leakage through malformed IP address representations. This issue affects versions prior to 7.15.2 and 8.0.1, creating a scenario where cookies intended for specific IP addresses can be inadvertently shared across subdomains due to inconsistent parsing of numeric IP literals. The core technical problem stems from how the function processes domain strings without proper validation of their numeric format, leading to discrepancies between Guzzle's cookie handling and standard HTTP client behavior such as libcurl.
The vulnerability manifests when cookies are set with IP address literals in various numeric bases including hexadecimal and octal representations. Specifically, when a cookie is set with Domain=0x7f000001, the function fails to recognize this as an IP literal and instead treats it as a regular domain name. This allows cookies to be matched against subdomains of the same numeric representation, creating a security boundary violation where session identifiers or tokens can be transmitted to unintended hosts. The flaw is particularly dangerous because it exploits the difference between how Guzzle parses these addresses versus how established HTTP clients like libcurl handle them, with libcurl correctly interpreting 0x7f000001 as 127.0.0.1 while Guzzle does not.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable session hijacking and cross-site request forgery attacks. When an application enables cookie support and makes requests using these malformed IP address representations, attackers can exploit the inconsistency to inject cookies into requests meant for different hosts. This allows malicious actors who control domains like evil.0x7f000001 to receive session identifiers or tokens that were originally intended for 127.0.0.1, effectively bypassing domain security boundaries. The vulnerability creates a persistent threat where responses from these look-alike domains can set cookies that are then replayed to the actual IP address, enabling attackers to manipulate application state and potentially gain unauthorized access.
The technical implementation flaw aligns with CWE-284 (Improper Access Control) and CWE-1107 (Improper Handling of Multiple Numeric Forms for IP Addresses) categories, as it represents a failure in access control mechanisms that should prevent cross-domain cookie leakage. Additionally, this vulnerability maps to ATT&CK technique T1589.002 (Credential Access: Steal Application Access Token) and T1071.004 (Application Layer Protocol: DNS) since it enables unauthorized access through malformed domain representations and leverages DNS resolution behaviors. The security implications are particularly severe in environments where applications make requests to hosts using various numeric IP address formats, as the vulnerability can be exploited even when the application appears to function correctly with standard HTTP operations.
Mitigation strategies should focus on upgrading to Guzzle versions 7.15.2 or 8.0.1 where the domain matching logic has been corrected to properly identify and handle IP address literals across different numeric bases. Organizations should also implement strict input validation for cookie domain parameters and consider implementing additional security measures such as SameSite cookie attributes, secure flag enforcement, and comprehensive monitoring of cookie-related HTTP traffic. The fix addresses the root cause by ensuring consistent parsing of numeric IP representations and proper domain matching behavior that aligns with standard HTTP client implementations. Security teams should conduct thorough testing to ensure that all applications using Guzzle are updated and that existing sessions are invalidated to prevent exploitation of this vulnerability across their infrastructure.