ALPINE-CVE-2026-56444
In NLnet Labs Unbound 1.20.0 up to and including 1.25.1, when Unbound is configured with 'serve-expired: yes' and 'serve-expired-client-timeout > discard-timeout > 0' (contrary to the suggested values), the discard-timeout branch during the serve expired logic drops an aged client reply without performing the correct accounting for the number of reply addresses for the query. Other identical branches outside of serve expired perform the correct decrement. Since the counter is never decremented in such scenario, it can reach the maximum limit and new clients for duplicate in-flight queries are silently dropped resulting in degradation of resolution service. A malicious actor can exploit the vulnerability by querying the resolver for a client-controlled slow-on-demand authoritative zone that can drive the counter past the threshold. Shipped defaults for 'serve-expired-client-timeout: 1800' and 'discard-timeout: 1900' make the branch unreachable.
ALPINE-CVE-2026-56444
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:ALPINE-CVE-2026-56444
unbound
Source reference: /affected/0/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.25.2-r0
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
unbound
Source reference: /affected/1/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.25.2-r0
Source reference:
/affected/1/ranges - Prerequisites
- Not stated in this record
unbound
Source reference: /affected/2/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.25.2-r0
Source reference:
/affected/2/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "1.20.0"
},
{
"fixed": "1.25.2-r0"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:apk/alpine/unbound?arch=source",
"ecosystem": "Alpine:v3.22"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-56444.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "1.20.0"
},
{
"fixed": "1.25.2-r0"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:apk/alpine/unbound?arch=source",
"ecosystem": "Alpine:v3.23"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-56444.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "1.20.0"
},
{
"fixed": "1.25.2-r0"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:apk/alpine/unbound?arch=source",
"ecosystem": "Alpine:v3.24"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-56444.json"
},
"ecosystem_specific": {}
}
]Publisher severity
No explicit severity was provided.
- Event
- #54558 · Revision 1
- Added to Heist Feed
- Publisher date