vulnerability / NVI-00010703 / Revision 5
fastify is vulnerable to header validation bypass via case-sensitive propertyNames
GitHub lists this reviewed advisory for fastify. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
3.7 low
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
3.7 LOW (3.1)
ce714d77-add3-4f53-aff5-83d477b104bb severity; no combined Null risk score.
0.257%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.17494. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
fastify
source listed>= 5.12.2, < 5.12.6
### Impact Fastify lowercases header names in a `headers` schema before compilation, because Node.js stores request header names in lowercase. This normalization does not reach the header names held in a `propertyNames` subschema's `enum` and `const`. A header-name deny-list written in the canonical header case, such as `propertyNames: { not: { enum: ['X-Debug-Override'] } }`, therefore never matches the lowercased request headers, and the forbidden header reaches the handler. Any application that uses a `propertyNames` deny-list or allow-list to constrain request header names does not get the constraint it expects. The same rule written in lowercase works, and the `not: { required: [...] }` form is unaffected, so this is a gap in the built-in normalization rather than a wrong schema. This is an incomplete fix of CVE-2026-84428 (GHSA-9q9j-q6p8-xq58), whose normalization covered header names used as property keys but not those used as values inside `propertyNames`. ### Patches Users should upgrade to fastify `5.12.6` or later, which lowercases header names held in `enum` and `const` inside a `propertyNa
fastify
source listedSEMVER: introduced 5.12.2; fixed 5.12.6
### Impact Fastify lowercases header names in a `headers` schema before compilation, because Node.js stores request header names in lowercase. This normalization does not reach the header names held in a `propertyNames` subschema's `enum` and `const`. A header-name deny-list written in the canonical header case, such as `propertyNames: { not: { enum: ['X-Debug-Override'] } }`, therefore never matches the lowercased request headers, and the forbidden header reaches the handler. Any application that uses a `propertyNames` deny-list or allow-list to constrain request header names does not get the constraint it expects. The same rule written in lowercase works, and the `not: { required: [...] }` form is unaffected, so this is a gap in the built-in normalization rather than a wrong schema. This is an incomplete fix of CVE-2026-84428 (GHSA-9q9j-q6p8-xq58), whose normalization covered header names used as property keys but not those used as values inside `propertyNames`. ### Patches Users should upgrade to fastify `5.12.6` or later, which lowercases header names held in `enum` and `const` inside a `propertyNa
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
- vendor patch
The original advisory lists fixed boundaries 5.12.6 for fastify. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
- NVD lastModified does not establish freshness of every associated CPE record.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-389g-gv7q-r4x8 ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- GHSA-389g-gv7q-r4x8 ↗
GitHub Advisory Database via OSV · vendor advisory
Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.
- CVE-2026-107832 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
- CVE-2026-107832 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 5 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 4 ·
Source facts changed; compare the preserved prior revision.
- Revision 3 ·
Source facts changed; compare the preserved prior revision.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.