Busybox: busybox: httpd silently fails open when ip deny rules contain invalid cidr prefix lengths (CVE-2026-88831) | HOL Guard CVE

Medium · CVSS 5.3CVE-2026-88831

Busybox: busybox: httpd silently fails open when ip deny rules contain invalid cidr prefix lengths

Answer in brief

CVE-2026-88831 records a Medium severity (CVSS 5.3) vulnerability in Busybox: busybox: httpd silently fails open when ip deny rules contain invalid cidr prefix lengths. The current sources do not mark it as known exploited. Affected software not mapped in the current feed; confirm the named product and version against your inventory.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 23, 2026Updated Sep 23, 2026Source checked Sep 23, 2026First seen by HOL Sep 23, 2026Material review Sep 23, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.3
Exploitation: Not marked as known exploited
Affected software: Not mapped
Fix availability: Not reported

Why this deserves its current priority

CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

Affected software not mapped in the current feed; confirm the named product and version against your inventory.

Recommended response

Confirm exposure. Identify whether the named product or interface exists in your inventory, then review the linked upstream references for affected versions and vendor guidance.

Evidence timeline and material changes

Published upstream
Sep 23, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 23, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 23, 2026

Sources and claim methodology

Upstream source description

BusyBox httpd IP deny rules with invalid CIDR prefix lengths fail open, leaving a parsed IP with a zeroed mask so the rule matches no clients.

Quoted source text, attributed separately from HOL analysis.