MinIO is a high-performance object storage system. Starting in RELEASE.2023-05-18T00-05-36Z and prior to RELEASE.2026-04-11T03-20-12Z, an authentication bypass vulnerability in MinIO's Snowball auto-extract handler (PutObjectExtractHandler) allows any user who knows a valid access key to write arbitrary objects to any bucket without knowing the secret key or providing a valid cryptographic signature. Any MinIO deployment is impacted. The attack requires only a valid access key (the well-known default minioadmin, or any key with WRITE permission on a bucket) and a target bucket name. When authTypeStreamingUnsignedTrailer support was added, the new auth type was handled in PutObjectHandler and PutObjectPartHandler but was never added to PutObjectExtractHandler. The snowball auto-extract handler's switch rAuthType block has no case for authTypeStreamingUnsignedTrailer, so execution falls through with zero signature verification. The isPutActionAllowed call before the switch extracts the access key and checks IAM permissions, but does not verify the cryptographic signature. An attacker sends a PUT request with X-Amz-Content-Sha256: STREAMING-UNSIGNED-PAYLOAD-TRAILER, X-Amz-Meta-Snowball-Auto-Extract: true, and an Authorization header containing a valid access key with a completely fabricated signature. The request is accepted and the tar payload is extracted into the bucket. Users of the open-source minio/minio project should upgrade to MinIO AIStor RELEASE.2026-04-11T03-20-12Z or later. If upgrading is not immediately possible, block unsigned-trailer requests at the load balancer. Reject any request containing X-Amz-Content-Sha256: STREAMING-UNSIGNED-PAYLOAD-TRAILER at the reverse proxy or WAF layer. Clients can use STREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER (the signed variant) instead. Alternatively, restrict WRITE permissions. Limit s3:PutObject grants to trusted principals. While this reduces the attack surface, it does not eliminate the vulnerability since any user with WRITE permission can exploit it with only their access key.
CVE-2026-40344
“—” beside the score: it is equal to NVD's CVSS score.
Score 8.2 from GitHub Security Advisory (severity: HIGH) published 2026-04-14. NVD baseline CVSS 8.2; sources differ by 0.0.
Also known asEUVD-2026-24579 (ENISA EUVD) · GHSA-9c4q-hq6p-c237 (GitHub Security Advisories)Source: ENISA EUVD
- High severity, but no confirmed exploitation yet
A fix is referenced (a reference tagged "Patch", often a source commit), but no release containing it is confirmed — find the release that contains it; until it is applied, mitigate (WAF / firewall / segmentation).
- CVSS v3
- 8.2
- EG Score
- 8.2HIGHmedium confidence
- EG Risk
- 52EG Risk 52/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity82% × 45%Impact severity (EG Severity): CVSS 8.2 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.7% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability100% × 15%CISA's SSVC Automatable value: yes (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it and apply that within your standard update timelines at low or medium mission impact and sooner than that at high; until then, restrict network exposure of the affected system or apply the vendor's mitigation. - EPSS PROB
- 0.4%
- EPSS %ILE
- 36th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (8.2): severity, escalated by confirmed exploitation. This CVE's 8.2 is its impact severity (EG Severity), not escalated.
- EG Severity
- 8.2 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.4% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it and apply that within your standard update timelines at low or medium mission impact and sooner than that at high; until then, restrict network exposure of the affected system or apply the vendor's mitigation.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
April 22, 2026
Last Modified
April 27, 2026
Advisory Details (3)
Auto-updated May 3, 2026Unauthenticated Object Write via Missing Signature Verification in Snowball Auto-Extract · Advisory · minio/minio · GitHub
https://github.com/minio/minio/security/advisories/GHSA-9c4q-hq6p-c237Signed trailers for signature v4 by klauspost · Pull Request #16484 · minio/minio · GitHub
https://github.com/minio/minio/pull/16484Signed trailers for signature v4 (#16484) · minio/minio@76913a9 · GitHub
https://github.com/minio/minio/commit/76913a9fd5c6e5c2dbd4e8c7faf56ed9e9e24091Patch Availability(1)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| go | github.com/minio/minio | — | ghsa |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(1 across 1 ecosystem)
Go(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| github.com/minio/minio | — |
| — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 40× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 99 of 242 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 100 is merged into the row it repeats. The 143 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-10-25 14:31 UTCEG score recompute
- 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
- 2026-10-24 13:44 UTCEG score recompute
- 2026-10-24 13:44 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-18 03:43 UTCEG score recompute
- 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-17 14:52 UTCEG score recompute
- 2026-10-17 14:52 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-12 16:09 UTCEG score recompute
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- 2026-10-11 19:51 UTCEG score recompute
- 2026-10-11 17:05 UTCEG score recompute
- 2026-10-11 14:31 UTCEG score recompute
- 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-10 18:25 UTCOSV refresh
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.7% · 51st percentile
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.7% · 51st percentile
- 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.7% · 51st percentile
- 2026-09-21 05:49 UTCOSV refresh
- 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-09-02 03:09 UTCOSV refresh
- 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.4% · 35th percentile
- 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-16 06:04 UTCEG score recompute
- 2026-08-16 06:04 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-14 16:03 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-08-14 04:22 UTCEG score recompute
- 2026-08-14 04:22 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-13 08:40 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-08-12 18:34 UTCEG score recompute
- 2026-08-12 18:34 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-11 16:48 UTCEG score recompute
- 2026-08-11 16:48 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-08-11 13:43 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-11 02:23 UTCEG score recompute
- 2026-08-11 02:23 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-10 02:58 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-08-09 15:17 UTCEG score recompute
- 2026-08-09 15:17 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
- 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.4% · 34th percentile
- 2026-08-09 03:36 UTCEG score recompute
- 2026-08-09 03:36 UTCGHSA enrichmentGHSA-9c4q-hq6p-c237 · GitHub severity HIGH · GitHub CVSS 8.2
Related CVEs(same product + same CWE)
Same product
10 shownGo:github.com/minio/minio
Same CWE
10 shownCWE-287 · CWE-306
Frequently asked(5)
What is CVE-2026-40344?
When was the CVE record for CVE-2026-40344 published?
Is CVE-2026-40344 actively exploited?
What is the CVSS score of CVE-2026-40344?
How do I remediate CVE-2026-40344?
Dependency Blast Radius
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