Security readout for executives and security teams
Plain-English summary
This flaw affects older WhatsApp mobile, KaiOS, and Desktop clients. A malicious 1:1 call scenario could trigger memory corruption, with CVSS-rated impact to confidentiality, integrity, and availability. The practical priority is removing outdated WhatsApp versions from managed or business-used devices.
Executive priority
Treat this as a high-priority hygiene and exposure-reduction issue. The severity is critical, the affected product is widely used, and remediation appears version-based. Prioritize managed devices and business accounts first.
Technical view
CVE-2021-24042 is an out-of-bounds write in WhatsApp calling logic, mapped to CWE-122 and CWE-787. The vulnerable condition cited is a user making a 1:1 call to a malicious actor. The CVSS 3.1 score is 9.8 with network attack vector and high CIA impact.
Likely exposure
Exposure is likely where users run WhatsApp for Android, WhatsApp Business for Android, WhatsApp for iOS, WhatsApp Business for iOS, WhatsApp for KaiOS, or WhatsApp Desktop below the fixed versions named by WhatsApp.
Exploitation context
The provided bundle does not show CISA KEV listing or cited evidence of active exploitation. Public evidence here supports a critical memory-corruption risk in a malicious call context, but not observed exploitation in the wild.
Researcher notes
The source bundle gives a concise vendor description but no exploit narrative, patch diff, or operational indicators. Note the description’s user-call condition when assessing reachability, and avoid claiming active exploitation without KEV or other cited evidence.
Mitigation direction
- Update WhatsApp for Android and Business for Android to v2.21.23 or later.
- Update WhatsApp for iOS and Business for iOS to v2.21.230 or later.
- Update WhatsApp for KaiOS to v2.2143 or later.
- Update WhatsApp Desktop to v2.2146 or later.
- Check WhatsApp’s advisory for any platform-specific guidance.
- Remove or block outdated clients on managed devices.
Validation and detection
- Inventory WhatsApp versions across managed mobile, KaiOS, and desktop endpoints.
- Confirm all installed clients meet or exceed the fixed versions.
- Check MDM, EDR, and software inventory for unmanaged outdated installs.
- Verify business users are not relying on unsupported legacy clients.
- Review vendor advisory records before closing remediation.
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-122: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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 lookupCWE-787: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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-2021-24042 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
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.whatsapp.com/security/advisories/2021/CVE 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.
Heap-based Buffer Overflow
Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Out-of-bounds Write
Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.