Security readout for executives and security teams
Plain-English summary
CVE-2026-27700 affects Hono applications using versions 4.12.0 or 4.12.1 with the AWS Lambda adapter behind an AWS Application Load Balancer. An attacker may spoof the client IP seen by the application and bypass IP-based access controls. The vendor patched this in Hono 4.12.2.
Executive priority
Treat as high priority where Hono protects administrative, internal, or sensitive routes by source IP. The issue can undermine trust boundaries without credentials. Organizations not using Hono on AWS Lambda behind ALB, or not using IP restrictions, are less likely to be exposed.
Technical view
In hono/aws-lambda, getConnInfo() selected the first X-Forwarded-For value. AWS ALB appends the real client IP at the end, so the first value can be attacker-controlled. Applications relying on getConnInfo(), including ipRestriction middleware, may make authorization decisions using a spoofed IP. Affected versions are >=4.12.0 and <4.12.2.
Likely exposure
Exposure is limited to Hono 4.12.0 or 4.12.1 applications using the AWS Lambda adapter behind an AWS Application Load Balancer and relying on IP-based access control from connection information.
Exploitation context
The CVE record rates this CVSS 8.2 with network attack vector, low complexity, no privileges, and no user interaction. The provided sources do not report active exploitation, and CISA KEV status is false in the bundle.
Researcher notes
Key condition is ALB X-Forwarded-For ordering: AWS ALB appends the real client IP, while affected Hono versions read the first value. Review commit 41adbf56e252c04611f8972364ac0887ae07a4c7 and advisory GHSA-xh87-mx6m-69f3 for the authoritative fix context.
Mitigation direction
- Upgrade Hono to version 4.12.2 or later.
- Prioritize applications using hono/aws-lambda behind AWS ALB.
- Review any ipRestriction or custom IP-based authorization logic.
- Check vendor advisory and release notes for implementation details.
Validation and detection
- Inventory package manifests and lockfiles for Hono versions 4.12.0 and 4.12.1.
- Identify deployments using AWS Lambda adapter behind Application Load Balancer.
- Confirm IP-based access controls do not depend on spoofable header ordering.
- Verify production builds include Hono 4.12.2 or later.
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
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ATT&CK lookup starting points
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CWE-290: Exact CWE lookup
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Open ATT&CK lookupCWE-345: 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-2026-27700 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.2 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/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:N/S:U/C:H/I:L/A:N3.94.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.2HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/honojs/hono/security/advisories/GHSA-xh87-mx6m-69f3CVE reference · x_refsource_CONFIRM
- https://github.com/honojs/hono/commit/41adbf56e252c04611f8972364ac0887ae07a4c7CVE reference · x_refsource_MISC
- https://github.com/honojs/hono/releases/tag/v4.12.2CVE 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.
Authentication Bypass by Spoofing
Authentication Bypass by Spoofing represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Insufficient Verification of Data Authenticity
Insufficient Verification of Data Authenticity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.