Security readout for executives and security teams
Plain-English summary
CVE-2021-4274 is a low-severity cross-site scripting issue in sileht bird-lg. The flaw involves request arguments rendered through templates/layout.html. Successful abuse requires user interaction and low privileges, and the documented impact is limited to integrity. Sources name an upstream patch, but do not provide affected version ranges.
Executive priority
Treat as a routine remediation item unless bird-lg is externally exposed or used in sensitive operational workflows. The issue is low severity, but XSS can still affect trust in administrative interfaces and should be patched during the next normal maintenance window.
Technical view
The CVE describes improper neutralization in bird-lg templates/layout.html where manipulation of request_args can lead to XSS. CVSS 3.1 is 3.5: network-accessible, low complexity, low privileges required, user interaction required, unchanged scope, no confidentiality or availability impact, low integrity impact.
Likely exposure
Exposure is limited to deployments of sileht bird-lg that have not incorporated commit ef6b32c527478fefe7a4436e10b96ee28ed5b308 or an equivalent vendor fix. The source bundle lists affected versions as n/a and provides no CPEs, so version-based exposure cannot be determined from these sources alone.
Exploitation context
The CVE says remote initiation is possible, but CVSS requires low privileges and user interaction. The source bundle marks KEV as false and provides no cited evidence of active exploitation, public weaponization, or exploitation at scale.
Researcher notes
The main uncertainty is affected versioning: the bundle lists versions as n/a and no CPEs. Analysis should focus on code lineage around templates/layout.html and the named patch. Do not assume broader products, branches, or exploitation activity without additional vendor or threat-intelligence evidence.
Mitigation direction
- Apply upstream patch commit ef6b32c527478fefe7a4436e10b96ee28ed5b308 or a release containing it.
- Review GitHub PR #82 for the vendor-intended fix context.
- Check vendor or project guidance for supported fixed versions.
- Prioritize remediation where bird-lg is internet-accessible or used by multiple operators.
Validation and detection
- Inventory all sileht bird-lg deployments and source revisions.
- Confirm the deployment includes commit ef6b32c527478fefe7a4436e10b96ee28ed5b308 or equivalent changes.
- Review templates/layout.html handling of request_args for proper output neutralization.
- Run approved XSS regression tests covering request argument rendering.
- Confirm no unsupported fork reverted or bypassed the upstream fix.
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-707: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-4274 mapping review
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Open ATT&CK lookup- Severity
- Low
- CVSS
- 3.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/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:L/UI:R/S:U/C:N/I:L/A:N2.11.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
3.5LowVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/sileht/bird-lg/pull/82CVE reference
- https://github.com/sileht/bird-lg/commit/ef6b32c527478fefe7a4436e10b96ee28ed5b308CVE reference
- https://vuldb.com/?id.216479CVE reference
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 Neutralization
Improper Neutralization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.