Security readout for executives and security teams
Plain-English summary
Synology Calendar versions before 2.4.0-0761 contained hard-coded credentials in a PHP component. A remote attacker could obtain sensitive information through unspecified vectors. The known impact is confidentiality exposure, not data tampering or service disruption.
Executive priority
Treat this as a medium-priority confidentiality issue. It should be remediated in normal patch cycles, faster for internet-facing Synology Calendar deployments or environments handling sensitive scheduling data.
Technical view
CVE-2021-34812 is CWE-798 in Synology Calendar before 2.4.0-0761. CVSS 3.1 is 5.8: network-accessible, low complexity, no privileges or user interaction, scope changed, low confidentiality impact, no integrity or availability impact.
Likely exposure
Organizations running Synology Calendar below 2.4.0-0761 are potentially exposed, especially if the service is reachable from the internet or untrusted networks. The source bundle does not provide CPEs, platform details, or exact vulnerable build ranges beyond the fixed version boundary.
Exploitation context
The source bundle does not indicate CISA KEV listing or active exploitation. The vulnerability is remotely reachable and unauthenticated by CVSS, but the attack vectors are unspecified, so practical exploitability cannot be assessed from the provided evidence.
Researcher notes
Public details are sparse. The sources identify hard-coded credentials in a PHP component and sensitive information disclosure, but do not describe the credential, affected code path, exploit method, or concrete data exposed.
Mitigation direction
- Upgrade Synology Calendar to version 2.4.0-0761 or later.
- Review Synology advisory Synology_SA_21_12 for official package guidance.
- Restrict Synology Calendar exposure to trusted networks where possible.
- Confirm backups and recovery procedures before applying updates.
- Monitor for unusual access to Calendar data after remediation.
Validation and detection
- Inventory all Synology Calendar deployments and record installed versions.
- Flag any instance running below 2.4.0-0761 as vulnerable.
- Check whether Calendar is reachable from the internet or untrusted networks.
- Verify the updated package version after remediation.
- Review logs for unusual Calendar access around the exposure window.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-798: Credential and account abuse lookup
Authentication and credential weaknesses can make valid-account abuse and credential telemetry useful review starting points. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-34812 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.8MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.synology.com/security/advisory/Synology_SA_21_12CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Use of Hard-coded Credentials
Use of Hard-coded Credentials represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.