CVE-2026-42882

CRITICALNVD 9.49.4
EchelonGraph scoreMEDIUM confidence

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

Score 9.4 from GitHub Security Advisory (severity: CRITICAL) published 2026-05-05. NVD baseline CVSS 9.4; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Elevated

Also known asEUVD-2026-29205 (ENISA EUVD) · GHSA-rfgq-wgg8-662p (GitHub Security Advisories) · GO-2026-5616 (OSV.dev)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.GitHub Security Advisory CVSS
EG Likelihood
0.6% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). 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, and whom BOD 26-04 binds: 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.

The score's inputs: 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

Vendor Advisories for CVE-2026-42882(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
gogithub.com/oxyno-zeta/s3-proxy @ 0.0.0-20260424211602-1320e4abd46a (fixes < 0.0.0-20260424211602-1320e4abd46a)—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)
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 14× in last 7d / 44× 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 its CVE.org record (CNA or CISA ADP). 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). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 253 rows 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 153 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-13 09:41 UTCEchelonGraph re-scored
  2. 2026-11-13 09:41 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  3. 2026-11-12 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  4. 2026-11-12 10:13 UTCEchelonGraph re-scored
  5. 2026-11-12 10:12 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  6. 2026-11-11 16:39 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  7. 2026-11-11 10:38 UTCEchelonGraph re-scored
  8. 2026-11-11 10:38 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  9. 2026-11-10 16:44 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  10. 2026-11-10 11:09 UTCEchelonGraph re-scored
  11. 2026-11-10 11:09 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  12. 2026-11-09 16:35 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  13. 2026-11-09 11:40 UTCEchelonGraph re-scored
  14. 2026-11-09 11:40 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  15. 2026-11-08 16:39 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  16. 2026-11-08 12:11 UTCEchelonGraph re-scored
  17. 2026-11-08 12:11 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  18. 2026-11-07 16:39 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  19. 2026-11-07 12:39 UTCEchelonGraph re-scored
  20. 2026-11-07 12:39 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  21. 2026-11-06 16:38 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  22. 2026-11-06 13:11 UTCEchelonGraph re-scored
  23. 2026-11-06 13:11 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  24. 2026-11-06 08:55 UTCOSV refresh
  25. 2026-11-05 16:37 UTCEPSS rescoreEPSS 0.6% · 46th percentile
Show 75 more
  1. 2026-11-05 13:41 UTCEchelonGraph re-scored
  2. 2026-11-05 13:41 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  3. 2026-11-04 16:35 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  4. 2026-11-04 14:12 UTCEchelonGraph re-scored
  5. 2026-11-04 14:12 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  6. 2026-11-03 16:48 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  7. 2026-11-03 14:43 UTCEchelonGraph re-scored
  8. 2026-11-03 14:43 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  9. 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  10. 2026-11-02 14:55 UTCEchelonGraph re-scored
  11. 2026-11-02 14:55 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  12. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  13. 2026-11-01 15:26 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  14. 2026-11-01 07:50 UTCGHSA enrichmentGHSA-rfgq-wgg8-662p · GitHub severity CRITICAL · GitHub CVSS 9.4
  15. 2026-11-01 07:50 UTCEchelonGraph re-scored
  16. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  17. 2026-10-31 15:57 UTCEchelonGraph re-scored
  18. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  19. 2026-10-29 17:00 UTCEchelonGraph re-scored
  20. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  21. 2026-10-28 17:30 UTCEchelonGraph re-scored
  22. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  23. 2026-10-27 17:58 UTCEchelonGraph re-scored
  24. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  25. 2026-10-26 18:29 UTCEchelonGraph re-scored
  26. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  27. 2026-10-26 12:04 UTCEchelonGraph re-scored
  28. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.6% · 46th percentile
  29. 2026-10-25 14:28 UTCEchelonGraph re-scored
  30. 2026-10-25 12:31 UTCEchelonGraph re-scored
  31. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  32. 2026-10-24 13:00 UTCEchelonGraph re-scored
  33. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  34. 2026-10-23 13:32 UTCEchelonGraph re-scored
  35. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  36. 2026-10-22 13:57 UTCEchelonGraph re-scored
  37. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  38. 2026-10-21 14:28 UTCEchelonGraph re-scored
  39. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  40. 2026-10-20 14:36 UTCEchelonGraph re-scored
  41. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.7% · 53rd percentile
  42. 2026-10-19 13:41 UTCEchelonGraph re-scored
  43. 2026-10-18 03:40 UTCEchelonGraph re-scored
  44. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  45. 2026-10-17 14:16 UTCEchelonGraph re-scored
  46. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  47. 2026-10-16 14:47 UTCEchelonGraph re-scored
  48. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  49. 2026-10-15 15:16 UTCEchelonGraph re-scored
  50. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  51. 2026-10-14 09:40 UTCEchelonGraph re-scored
  52. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  53. 2026-10-13 07:27 UTCEchelonGraph re-scored
  54. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  55. 2026-10-12 16:07 UTCEchelonGraph re-scored
  56. 2026-10-11 19:48 UTCEchelonGraph re-scored
  57. 2026-10-11 17:03 UTCEchelonGraph re-scored
  58. 2026-10-11 14:29 UTCEchelonGraph re-scored
  59. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  60. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  61. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  62. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  63. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  64. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  65. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  66. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  67. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  68. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  69. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  70. 2026-09-30 06:58 UTCOSV refresh
  71. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  72. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  73. 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  74. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.6% · 45th percentile
  75. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.6% · 45th percentile

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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. The vendor advisories EchelonGraph has for CVE-2026-42882 are linked in the Vendor Advisories panel on this page.

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