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Threats / Apache / CVE-2019-17558
CVE-2019-17558 · EUVD no mirror located · GCVE no mirror located Verified 2026-06-07

Apache Solr vulnerability

Apache Solr VelocityResponseWriter plug-in contains an unspecified vulnerability allowing remote code execution through improper input handling.

Verdict

Today item — known-exploited.

An unauthenticated attacker can execute arbitrary code on affected Solr instances by exploiting unsafe template processing in the VelocityResponseWriter component. Active exploitation in the wild indicates immediate risk.

CISA KEV Yes · 2021-11-033EPSS 0.9447 (verify live)4
01

Is it exploitable?

— the evidence, ranked above the score
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
CISA KEV ↗Confirmed
Probability (EPSS)
EPSS 0.9447 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
FIRST EPSS ↗High
Severity / affected
Affected: Apache, Solr. Confirm exact fixed builds in the vendor advisory.
NVD ↗Reported
Weakness (CWE)
Mapped to CWE-74 CWE-74 — weakness family: Injection.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
NVD ↗Reported
WeaknessCWE-74 · CWE-74Injection
02

Who’s exploiting it?

— attribution turns risk into urgency
Attribution not established

No threat-actor attribution is established from the public feed for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.

03

Why it matters

— the attack path, told twice: adversary, then board
1

Front door — unauthenticated access narrative 1

Attacker
I craft a malicious request containing code injection payloads targeting the VelocityResponseWriter template engine.
Business
Attackers gain unauthenticated remote code execution capability against internet-facing Solr deployments.
2

Keys to the kingdom — privilege/identity takeover narrative 2

Attacker
I send the payload through standard Solr query parameters without authentication requirements.
Business
Exploitation requires no credentials, dramatically expanding the attack surface across all exposed instances.
3

Lateral reach — past segmentation narrative 3

Attacker
I execute arbitrary system commands with the privileges of the Solr process.
Business
Compromised servers become entry points for lateral movement, data exfiltration, and infrastructure takeover.
04

What to do

— defensible action
  • Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05

Coverage & confidence

— what we know, and what we don’t

Established (cited)

  • KEV listing (CISA)
  • EPSS probability (FIRST)
  • CWE weakness mapping (NVD)
  • Catalogued by apache (CNA)

    • Coverage gaps — stated, not hidden

  • No EUVD / GCVE mirror in feed — single-authority dependency for the identifier.
  • EPSS & exposure are time-varying; verify live at the source.
  • Threat-actor attribution not established from feed data — absence of a name is not absence of compromise.
  • No finder/reporter credit recorded in the public CVE entry — the work behind this find is unattributed.
    • Disclosure & credit2
    Catalogued by apacheCNA
    Credited with finding itNo finder named in the public CVE record — the work behind this find is unattributed.