CVE-2026-25222
Published: 02 February 2026
Summary
CVE-2026-25222 is a medium-severity Exposure of Sensitive Information to an Unauthorized Actor (CWE-200) vulnerability in Polarlearn Polarlearn. Its CVSS base score is 6.3 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Email Addresses (T1589.002); ranked at the 12.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 IA-6 (Authentication Feedback) and SC-31 (Covert Channel Analysis).
Deeper analysis
CVE-2026-25222 is a timing attack vulnerability affecting PolarLearn, a free and open-source learning program, in versions 0-PRERELEASE-15 and earlier. The issue resides in the sign-in process, where unauthenticated attackers can determine if a specific email address is registered on the platform by measuring response times from the login endpoint. This discrepancy arises because the server performs computationally expensive Argon2 password hashing only for existing users, resulting in significantly longer response times—approximately 650ms for valid emails versus 160ms for non-existent ones. The vulnerability is rated with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) and maps to CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor).
Unauthenticated remote attackers can exploit this vulnerability over the network with low complexity and no privileges required. By sending repeated login requests with targeted email addresses and timing the responses, attackers can reliably enumerate valid user accounts registered on the platform. This enables harvesting of email lists, which could facilitate further attacks such as phishing, credential stuffing, or social engineering, though it does not allow direct access to passwords or other account data.
Mitigation is detailed in the PolarLearn GitHub security advisory (GHSA-wcr9-mvr9-4qh5) and addressed in commit 6c276855172c7310cce0df996cb47ffe0d886741, which likely implements consistent timing behavior in the authentication flow to prevent side-channel leakage. Security practitioners should update to a patched version beyond 0-PRERELEASE-15 and review login endpoints for similar timing oracle issues in custom implementations.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-5344
Vulnerability details
PolarLearn is a free and open-source learning program. In 0-PRERELEASE-15 and earlier, a timing attack vulnerability in the sign-in process allows unauthenticated attackers to determine if a specific email address is registered on the platform. By measuring the response time…
more
of the login endpoint, an attacker can distinguish between valid and invalid email addresses. This occurs because the server only performs the computationally expensive Argon2 password hashing if the user exists in the database. Requests for existing users take significantly longer (~650ms) than requests for non-existent users (~160ms).
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Timing side-channel directly enables remote enumeration of valid email addresses/accounts (T1589.002, T1087.003) without authentication.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires obscuring authentication feedback, including timing data from login attempts, to prevent attackers from distinguishing valid email addresses via response time discrepancies.
Mandates identification and mitigation of covert timing channels, precisely addressing the side-channel leakage of registered user existence through differential response times in the sign-in process.
Limits consecutive unsuccessful logon attempts and enforces account lockouts, impeding attackers from sending the multiple timed requests required for reliable user enumeration.