CVE-2026-55767: Guzzle is an extensible PHP HTTP client

Q: How do I fix CVE-2026-55767?

guzzle: upgrade to 7.12.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-55767 being exploited?

CVE-2026-55767 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-55767 affect?

CVE-2026-55767 affects guzzle. Severity is medium (CVSS 5.8). 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, normali

Q: How urgent is CVE-2026-55767?

Priority 28/100. Remotely exploitable, no login, no user action

Routine

MEDIUM 5.8REMOTEUPGRADE

CVE-2026-55767 is a medium-severity flaw (CVSS 5.8) affecting guzzle. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 89%)
CISA exploited list	No
Weakness	CWE-346, CWE-1286
Published	2026-06-23
Last modified	2026-08-05

Publisher (CNA): GitHub, Inc. · Vendor: guzzlephp

Last updated 2026-08-05 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-23 16:17 UTCPublished CVE record published
2026-08-05 22:17 UTCUpdated Record last modified

guzzlephp guzzle UPGRADE

Affected: < 7.12.1

Fixed in: 7.12.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy guzzle || rpm -q guzzle || guzzle --version

2. UPGRADE to 7.12.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade guzzle

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade guzzle

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-55767?

guzzle: upgrade to 7.12.1. Exact commands for each OS are on this page.

Is CVE-2026-55767 being exploited?

CVE-2026-55767 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-55767 affect?

CVE-2026-55767 affects guzzle. Severity is medium (CVSS 5.8). 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, normali

How urgent is CVE-2026-55767?

Priority 28/100. Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

Related CVEs

CVE-2026-59883 MEDIUM 4.7 UPGRADE Guzzle is an extensible PHP HTTP client
CVE-2026-55568 MEDIUM 5.9 UPGRADE Guzzle is an extensible PHP HTTP client

References

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