CVE-2026-26273: Known affected by Account Takeover via Password Reset Token Leakage

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 1.3%, percentile 70: FIRST’s model estimates a 1.3% chance of exploitation activity in the next 30 days, higher than 70% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes idno/known (Composer (PHP)) <= 1.6.2, fixed in 1.6.3. Check your lockfile, including transitive dependencies.

What it is

Known is a social publishing platform. Prior to 1.6.3, a Critical Broken Authentication vulnerability exists in Known 1.6.2 and earlier. The application leaks the password reset token within a hidden HTML input field on the password reset page. This allows any unauthenticated attacker to retrieve the reset token for any user by simply querying the user's email, leading to full Account Takeover (ATO) without requiring access to the victim's email inbox. This vulnerability is fixed in 1.6.3.

From the GitHub advisory

Summary A Critical Broken Authentication vulnerability exists in Known 1.6.2. The application leaks the password reset token within a hidden HTML input field on the password reset page. This allows any unauthenticated attacker to retrieve the reset token for any user by simply querying the user's email, leading to full Account Takeover (ATO) without requiring access to the victim's email inbox.

Details The vulnerability occurs within the password reset flow. When a reset is requested, the application generates a verification code. However, the subsequent reset page (/account/password/reset/) incorrectly reflects this code back to the client in the HTML source code.

Specifically, the sensitive token is embedded in:

Because this page is accessible via a GET request using the victim's email as a parameter, an attacker can programmatically extract the token.

PoC 1. The attacker asks for a password reset for the victim

Weakness type: CWE-200, CWE-640.

Product: idno/known (Composer (PHP)) · Assigned by: GitHub_M · Published: 2026-02-13

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 1.30% probability of exploitation activity in the next 30 days; percentile 70.

Timeline

• 2026-02-13 — CVE record published by GitHub_M
• 2026-02-13 — GitHub-reviewed advisory GHSA-78wq-6gcv-w28r published (critical)
• 2026-02-17 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-78wq-6gcv-w28r github.com
2. CVE.org record CVE-2026-26273 cve.org
3. NVD entry CVE-2026-26273 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

Critical Composer (PHP) advisories · Today’s Security Digest