Security readout for executives and security teams
Plain-English summary
Fastify can parse a request body while skipping the intended body validation when the Content-Type header is malformed with a leading space. For affected APIs, this can let invalid or unexpected input reach business logic, creating integrity risk in exposed services.
Executive priority
Treat as high priority for exposed APIs using Fastify body schema validation. The fix is a direct dependency upgrade, and delaying leaves business logic dependent on validation that may be bypassed.
Technical view
CVE-2026-33806 affects Fastify versions from 5.3.2 before 5.8.5 when applications use schema.body.content for per-content-type validation. A leading space in Content-Type can bypass validation while parsing still occurs. The issue is a regression from the CVE-2025-32442 fix.
Likely exposure
Exposure is most likely in Node.js services running affected Fastify 5.x versions, especially public APIs that depend on schema.body.content to enforce JSON or other body validation.
Exploitation context
The source bundle reports network exploitable, low-complexity, unauthenticated impact on integrity. KEV is false, and no provided source states active exploitation. Evidence supports validation bypass risk, not confirmed exploitation in the wild.
Researcher notes
Focus analysis on schema.body.content behavior and affected Fastify 5.x dependency ranges. The bundle names no workaround and no active exploitation. Avoid broad claims about all Fastify validation paths without vendor evidence.
Mitigation direction
- Upgrade Fastify to v5.8.5 or later.
- Prioritize internet-facing APIs using schema.body.content validation.
- Update lockfiles and redeploy affected services.
- Do not rely on workarounds; sources state none are available.
- Track Fastify and OpenJS advisories for any follow-up guidance.
Validation and detection
- Inventory deployed Fastify versions across applications and containers.
- Identify routes using schema.body.content for request validation.
- Confirm affected services are upgraded to Fastify v5.8.5 or later.
- Run controlled regression tests for malformed Content-Type handling.
- Review logs for rejected or anomalous Content-Type values.
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-1287: Exact CWE lookup
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Open ATT&CK lookupCWE-1289: 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-2026-33806 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
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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.
SSVC decision data
CVSS vector scores
2 official scoresWe 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:N/I:H/A:N3.93.6openjsCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N3.93.6redhat-SADPVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- ADP timelineredhat-SADP
Made public.
- CVE publishedCVE Program
The CVE record was published.
- ADP timelineredhat-SADP
Reported to Red Hat.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-04-15T02:01:50.548Z: Reported to Red Hat.
- 2026-04-15T00:14:02.376Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/fastify/fastify/security/advisories/GHSA-mg2h-6x62-wpwcCVE reference, openjs
- https://cna.openjsf.org/security-advisories.htmlCVE reference, openjs
- https://access.redhat.com/security/cve/CVE-2026-33806CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2458596CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33806.jsonCVE reference, redhat-SADP · x_sadp-csaf-vex
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.
Improper Validation of Specified Type of Input
Improper Validation of Specified Type of Input represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improper Validation of Unsafe Equivalence in Input
Improper Validation of Unsafe Equivalence in Input represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.