Security readout for executives and security teams
Plain-English summary
CVE-2026-39087 affects ntfy before 2.22.0. A flawed web push endpoint URL check can let an unauthenticated remote attacker make the ntfy server send requests to unintended locations. That is server-side request forgery, which can expose internal services or data depending on network access.
Executive priority
Treat this as urgent for any exposed or production ntfy deployment. Upgrade validation should be prioritized because the issue is critical, remotely reachable, and unauthenticated according to the CVE data.
Technical view
The CVE describes SSRF caused by an unanchored regular expression validating web push endpoint URLs in ntfy before 2.22.0. The record assigns CVSS 9.8 with network attack, low complexity, no privileges, and no user interaction. CWE mappings include CWE-777 and CWE-94, but public details in the bundle are limited.
Likely exposure
Exposure is most likely for organizations running self-hosted ntfy versions before 2.22.0, especially internet-reachable deployments or systems where ntfy can reach internal networks. The affected-version metadata is sparse, so confirm actual installed versions against vendor release information.
Exploitation context
The bundle does not show CISA KEV listing or other evidence of active exploitation. Risk remains high because the CVSS vector indicates unauthenticated remote exploitation with severe confidentiality, integrity, and availability impact if reachable.
Researcher notes
Public evidence in the bundle is limited to the CVE description, CVSS data, references, and the 2.22.0 release. Avoid assuming exploit maturity, affected configurations, or patch mechanics beyond ntfy before 2.22.0 and vendor guidance.
Mitigation direction
- Upgrade ntfy to version 2.22.0 or later.
- Review the ntfy 2.22.0 release notes and vendor guidance.
- Restrict ntfy outbound network access to required destinations only.
- Prioritize internet-facing or internally privileged ntfy deployments first.
Validation and detection
- Inventory all ntfy deployments and record installed versions.
- Confirm whether any instance runs a version before 2.22.0.
- Identify deployments with web push functionality exposed or enabled.
- Review outbound network telemetry from ntfy hosts for unusual destinations.
- Check vendor sources for updated advisories or backport guidance.
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-777: 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-94: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. 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 lookupCloud metadata behavior lookup
The CVE wording references SSRF or metadata access, so cloud discovery and credential material review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-39087 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.
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:H/I:H/A:H3.95.9CISA-ADPCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N3.12.7mitreVulnerability 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
Base CVSS 3.1 score
6.4MediumVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/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.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://gist.github.com/MightyNawaf/5d41d6e8ead16e217f86b016002ecae5CVE reference, mitre
- https://github.com/binwiederhier/ntfy/releases/tag/v2.22.0CVE reference, mitre
- https://ntfy.sh/CVE reference, mitre
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.
Regular Expression without Anchors
Regular Expression without Anchors represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improper Control of Generation of Code ('Code Injection')
Improper Control of Generation of Code ('Code Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.