CVE-2026-28318
SolarWinds Serv-U is susceptible to specially crafted POST requests that crash the Serv-U service without authentication using Content-Encoding: deflate. Mitigation steps are provided to secure customer environments in the SolarWinds Trust Center if you are unable to deploy the update
do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Can a WAF block it? Partly. The attack uses specially crafted HTTP POST requests with a specific Content-Encoding header to crash the service without authentication. A WAF could detect unusual or malformed deflate-encoded POST requests that differ from normal traffic. A custom WAF rule can filter POST requests with Content-Encoding: deflate causing service crash, but attackers can vary the request. No tracked WAF vendor has published a rule for this CVE yet.
What a custom rule would match: POST requests with Content-Encoding: deflate causing service crash
Also consider: patch · custom WAF rule · rate limit · CDN
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2026-28318 being exploited?
Yes. CVE-2026-28318 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2026-28318?
CVE-2026-28318 is rated High with a CVSS score of 7.5. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-28318?
Yes. A fix has been recorded for CVE-2026-28318. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-28318 affect?
CVE-2026-28318 affects solarwinds:serv-u. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
- affected<= 15.5.4
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
public exploits
Unvetted proof-of-concept code on GitHub: 2 GitHub proofs of concept
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
cisa ssvc
- exploitation
- active
- automatable
- yes
- technical impact
- partial
Assessed by CISA 5 Jun 2026 (SSVC 2.0.3).
timeline
- 4 Jun 2026Published
- 5 Jun 2026Added to CISA KEV (exploited in the wild) · same day later
- 5 Jun 2026CISA SSVC assessment: exploitation active · same day later
- 10 Jun 2026First proof-of-concept repository on GitHub (unvetted) · 5 days later
- 19 Jun 2026CISA remediation due date (US federal agencies) · 9 days later
- 21 Oct 2026CVE record last updated · 124 days (about 4 months) later
- 2 Nov 2026Analysed by vulneraibility.com · 12 days later
- Linksolarwinds.com /trust-center/security-advisories/CVE-2026-28318
- Linkdocumentation.solarwinds.com /en/success_center/servu/content/release_notes/servu_15-5-4-hotfix-1_release_not
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-28318
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- PoC-in-GitHub: GitHub repositories that claim a proof of concept
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.