Security readout for executives and security teams
Plain-English summary
CVE-2021-29624 affects fastify-csrf before 3.1.0. In multi-subdomain deployments, its cookie-based CSRF protection could be weakened by cookie tossing, potentially allowing unauthorized state-changing actions if a victim interacts with an attacker-controlled flow.
Executive priority
Treat this as a targeted integrity risk, not a broad emergency. Prioritize internet-facing authenticated Fastify applications using fastify-csrf on multi-subdomain infrastructure, especially where account, payment, admin, or profile changes are protected by CSRF tokens.
Technical view
The issue is CWE-565 in fastify-csrf's double-submit cookie design. For applications spread across subdomains, the CSRF token was not sufficiently bound to user-specific information. Version 3.1.0 adds support requiring users to pass userInfo when generating tokens for full protection.
Likely exposure
Exposure is most likely in Fastify applications using fastify-csrf versions below 3.1.0 and deployed across multiple subdomains or shared subdomain-style platforms. Single-domain deployments appear less directly affected based on the advisory text.
Exploitation context
The provided sources do not show CISA KEV listing or confirmed active exploitation. Attack feasibility depends on multi-subdomain hosting, cookie behavior, and user interaction, consistent with CVSS UI:R and high integrity impact.
Researcher notes
The key validation point is whether the application used vulnerable fastify-csrf versions and multi-subdomain cookie scope. The source bundle names the fixed version and implementation requirement, but does not provide evidence of exploitation in the wild.
Mitigation direction
- Upgrade fastify-csrf to version 3.1.0 or later.
- Pass userInfo when generating CSRF tokens for multi-subdomain applications.
- Review vendor advisory and release notes before deployment.
- Review OWASP CSRF guidance for double-submit cookie designs.
- Prioritize applications with authenticated state-changing actions.
Validation and detection
- Check package manifests and lockfiles for fastify-csrf versions below 3.1.0.
- Identify deployments using multiple subdomains or shared subdomain-style hosting.
- Review token generation code for required userInfo usage.
- Confirm CSRF protections still pass normal user workflows after upgrade.
- Verify no bundled or transitive legacy copy remains deployed.
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-565: 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 lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-29624 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
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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:R/S:U/C:N/I:H/A:N2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/fastify/fastify-csrf/security/advisories/GHSA-rc4q-9m69-gqp8CVE reference · x_refsource_CONFIRM
- https://github.com/fastify/csrf/pull/2CVE reference · x_refsource_MISC
- https://github.com/fastify/fastify-csrf/pull/51CVE reference · x_refsource_MISC
- https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.htmlCVE reference · x_refsource_MISC
- https://github.com/fastify/fastify-csrf/releases/tag/v3.1.0CVE reference · x_refsource_MISC
- https://owasp.org/www-pdf-archive/David_Johansson-Double_Defeat_of_Double-Submit_Cookie.pdfCVE reference · x_refsource_MISC
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.
Reliance on Cookies without Validation and Integrity Checking
Reliance on Cookies without Validation and Integrity Checking represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.