CVE-2026-42882

CRITICALNVD 9.49.4
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This critical-severity CVE scores 9.4 under NVD CVSS v3. EPSS exploit probability: 0.6% (46th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
Elevated

Also known asEUVD-2026-29205 (ENISA EUVD)Source: ENISA EUVD

9.4EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.6%CVSS: 9.4Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

oxyno-zeta/s3-proxy is an aws s3 proxy written in go. Prior to 5.0.0, s3-proxy contains an authentication bypass caused by inconsistent URL path interpretation between the authentication middleware and the bucket handler. The authentication middleware evaluates resource path patterns against the percent-encoded request URI (r.URL.RequestURI()), while the bucket handler constructs S3 object keys from the decoded path (r.URL.Path). This mismatch, combined with the glob library being invoked without a path separator (causing * to match across / boundaries), allows unauthenticated attackers to write to, read from, or delete objects in protected S3 namespaces. Exploitation is possible via three techniques: (1) using * patterns that match across path separators to reach protected routes via path traversal (e.g., /open/foo/drafts/../restricted/), (2) using percent-encoded slashes (%2F) to collapse multiple path segments into a single token at the auth layer while the decoded form resolves to a protected namespace at the storage layer, and (3) using dot-dot segments (../) under ** prefix patterns, where the raw path matches an open route while Go's URL parser resolves the traversal to a protected path before the bucket handler runs. An unauthenticated attacker with network access can perform unauthorized PUT, GET, or DELETE operations on objects in authentication-protected S3 namespaces. This vulnerability is fixed in 5.0.0.

CVSS v3
9.4
EG Score
9.4CRITICALmedium confidence
EG Risk
73
EG Risk 73/100

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)
Severity94% × 45%
Impact severity (EG Severity): CVSS 9.4 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (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 available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.6%
EPSS %ILE
46th
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 (9.4): severity, escalated by confirmed exploitation. This CVE's 9.4 is its impact severity (EG Severity), not escalated.

EG Severity
9.4 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.6% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-29). 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, Track* at medium and Attend at high mission impact.CISA BOD 26-04: 3 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, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (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)3 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 total (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

May 11, 2026

Last Modified

October 26, 2026

Advisory Details (3)

Auto-updated Oct 2, 2026
Patch available. Sources: github_commit, github.
GitHub advisoryMentions a patch (unverified)

Security Issues in Resource Path Matching · Advisory · oxyno-zeta/s3-proxy · GitHub

https://github.com/oxyno-zeta/s3-proxy/security/advisories/GHSA-rfgq-wgg8-662p
GitHub commit

commit af5ff57d8c60 (oxyno-zeta/s3-proxy)

Fix landed in oxyno-zeta/s3-proxy commit af5ff57d8c60 — awaiting tagged release

https://github.com/oxyno-zeta/s3-proxy/commit/af5ff57d8c6022459495b8fb50130073bca7b48a
GitHub commit

commit 1320e4abd46a (oxyno-zeta/s3-proxy)

Fix landed in oxyno-zeta/s3-proxy commit 1320e4abd46a — awaiting tagged release

https://github.com/oxyno-zeta/s3-proxy/commit/1320e4abd46ad18c2851fedde50dbb79df8b7a51

Affected Packages

(1 across 1 ecosystem)
Go(1)
PackageVulnerable rangeFix by version rangeDependents
github.com/oxyno-zeta/s3-proxy—
  • every version up to 0.0.0-20260424211602-1320e4abd46a: fixed in 0.0.0-20260424211602-1320e4abd46a
—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 15× in last 7d / 51× 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 100 of 210 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. None are among the latest 100 rows. The 110 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-29 17:00 UTCEG score recompute
  2. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  3. 2026-10-28 17:30 UTCEG score recompute
  4. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  5. 2026-10-27 17:58 UTCEG score recompute
  6. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.6% · 46th percentile
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  10. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
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  13. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
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  15. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
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  1. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  2. 2026-10-17 14:16 UTCEG score recompute
  3. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
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  5. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
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  7. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
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  9. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
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  11. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
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  14. 2026-10-11 17:03 UTCEG score recompute
  15. 2026-10-11 14:29 UTCEG score recompute
  16. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  17. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  18. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  19. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  20. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  21. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  22. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  23. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  24. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  25. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  26. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  27. 2026-09-30 06:58 UTCOSV refresh
  28. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  29. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  30. 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  31. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  32. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  33. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.6% · 44th percentile
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  36. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.6% · 44th percentile
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  38. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  39. 2026-09-11 11:53 UTCOSV refresh
  40. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  41. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  42. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  43. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  44. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.6% · 44th percentile
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  52. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  53. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  54. 2026-08-23 18:37 UTCEG score recompute
  55. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.6% · 44th percentile
  56. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
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  59. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
  60. 2026-08-17 14:55 UTCEG score recompute
  61. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.6% · 43rd percentile
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  74. 2026-08-11 01:10 UTCEG score recompute
  75. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.6% · 43rd percentile

Related CVEs(same product + same CWE)

Same product

1 shown

Go:github.com/oxyno-zeta/s3-proxy

Frequently asked(5)

What is CVE-2026-42882?
CVE-2026-42882 is a critical-severity vulnerability; its CVE record was published on May 11, 2026. oxyno-zeta/s3-proxy is an aws s3 proxy written in go. Prior to 5.0.0, s3-proxy contains an authentication bypass caused by inconsistent URL path interpretation between the authentication middleware and the bucket handler. The authentication middleware evaluates resource path patterns against the…
When was the CVE record for CVE-2026-42882 published?
The CVE record for CVE-2026-42882 was published on May 11, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 26, 2026; the record at its source may have been updated since.
Is CVE-2026-42882 actively exploited?
CVE-2026-42882 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.6% probability of exploitation in the next 30 days (46th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-42882?
CVE-2026-42882 has a CVSS v3 base score of 9.4 (NVD).
How do I remediate CVE-2026-42882?
A fix for CVE-2026-42882 is available: update to the fixed version the vendor names in its advisory.

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