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NVD / CVE Program· CNA NLnet Labs

CVE-2021-43173: Hanging RRDP request

HighCVSS 7.5 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 30/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.3% (FIRST EPSS); higher than 72.7% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: cfrpki (Debian:11) 1.4.2-1~deb11u1; fort-validator (Debian:11) 1.5.3-1~deb11u1; cfrpki (Debian:12) 1.4.0-1.

Low priority for now. Upgrade to cfrpki (Debian:11) 1.4.2-1~deb11u1; fort-validator (Debian:11) 1.5.3-1~deb11u1; cfrpki (Debian:12) 1.4.0-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In NLnet Labs Routinator prior to 0.10.2, a validation run can be delayed significantly by an RRDP repository by not answering but slowly drip-feeding bytes to keep the connection alive. This can be used to effectively stall validation. While Routinator has a configurable time-out value for RRDP connections, this time-out was only applied to individual read or write operations rather than the complete request. Thus, if an RRDP repository sends a little bit of data before that time-out expired, it can continuously extend the time it takes for the request to finish. Since validation will only continue once the update of an RRDP repository has concluded, this delay will cause validation to stall, leading to Routinator continuing to serve the old data set or, if in the initial validation run directly after starting, never serve any data at all.

Published
Nov 9, 2021
Updated
Jun 17, 2026
EPSS
1.3% · 72th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.3%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Follow CVE-2021-43173

When you'll hear from us

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  • when exploit code appears or is weaponized
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  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
nlnetlabsroutinator
debiandebian linux

Versions reported by the vendor

Affected version ranges reported by the assigning authority (NLnet Labs). Independent of NVD's CPE analysis and usually ahead of it.

  • NLnet Labs Routinator

    • unspecified and later · up to and including 0.10.1affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux11.0
  • nlnetlabs routinatorbefore 0.10.2

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:11cfrpkibefore 1.4.2-1~deb11u11.4.2-1~deb11u1
Debian:11fort-validatorbefore 1.5.3-1~deb11u11.5.3-1~deb11u1
Debian:12cfrpkibefore 1.4.0-11.4.0-1
Debian:12fort-validatorbefore 1.5.3-11.5.3-1
Debian:12rpki-clientbefore 7.5-17.5-1

Same product

nlnetlabs: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-49235Routinator crashes on specifically crafted RRDP XML files
    34Monitor
  • CVE-2026-49233Routinator cache path traversal using rogue rsync URIs
    33Monitor
  • CVE-2026-49234Routinator crashes on specifically crafted ASN strings in the API
    32Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-41531Sep 21, 2021 · Invalid RPKI data could disable Route Origin Validation on RTR clients.
    30Monitor
  • ← EarlierCVE-2021-43172Nov 9, 2021 · Infinite length chain of RRDP repositories
    30Monitor
  • Later →CVE-2021-43174Nov 9, 2021 · gzip transfer encoding caused out-of-memory crash
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:cfrpki1.4.0-1 · Debian:12Package registry (OSV)
debian:fort-validator1.5.3-1 · Debian:12Package registry (OSV)
debian:rpki-client7.5-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Not on record for this CVE: EPSS history · patch commit or PR link · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-755 · Improper Handling of Exceptional Conditions

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records