CVE-2026-6253

MEDIUMNVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

Score 5.9 from GitHub Security Advisory published 2026-05-13. NVD baseline CVSS 5.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 5 sources updated this weekElevated
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 5.9Exploit: Elevated riskExposed: 0

A fix is available — apply it.

curl might erroneously pass on credentials for a first proxy to a second proxy.

This can happen when the following conditions are true:

  • curl is setup to use specific different proxies for different URL schemes
  • the first proxy needs credentials
  • the second proxy uses no credentials
  • while using the first proxy (using say http://), curl is asked to follow
a redirect to a URL using another scheme (say https://), accessed using a second, different, proxy

CVSS v3
5.9
EG Score
5.9(medium)
EG Risk
43(Track)
EG Risk 43/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity59% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
52%
KEV
Not listed

Published

May 13, 2026

Last Modified

September 15, 2026

Advisory Details (4)

Auto-updated May 14, 2026
No patch confirmed yet.
generic

HackerOne

https://hackerone.com/reports/3669637
generic

oss-security - [ADVISORY] curl: CVE-2026-6253: proxy credentials leak over redirect-to proxy

http://www.openwall.com/lists/oss-security/2026/04/29/11
generic
https://curl.se/docs/CVE-2026-6253.json
generic

curl - proxy credentials leak over redirect-to proxy - CVE-2026-6253

https://curl.se/docs/CVE-2026-6253.html

Vendor Advisories for CVE-2026-6253(3)

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

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulibcurl4t64 (8.5.0-2ubuntu10.9) @ noble2026-09-15ubuntu
redhatpatch2026-08-19redhat
redhatcurl-main-8.20.0-0.1.hum12026-05-02redhat

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

(6 across 6 ecosystems)
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
curl—8.20.0-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
curl—8.20.0-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
curl7.74.0-1.3 ... 8.9.1-2~bpo12+1 (219 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
curl7.88.1-10 ... 8.9.1-2~bpo12+1 (178 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
curl8.14.1-2, 8.14.1-2+deb13u1, 8.14.1-2+deb13u2, 8.14.1-2+deb13u2~bpo13+1, 8.14.1-2+deb13u38.14.1-2+deb13u4—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
curl8.14.1-2 ... 8.20.0~rc2-1+exp1 (47 versions)8.20.0~rc3-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(1)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 10× in last 7d / 40× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. 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. Most recent first.

Showing the most recent 100 of 244 total refreshes for this CVE.

  1. 2026-09-15 07:26 UTCVendor advisory
  2. 2026-09-15 07:26 UTCGHSA enrichment
  3. 2026-09-15 06:39 UTCEG score recompute
  4. 2026-09-15 06:39 UTCVendor advisory
  5. 2026-09-15 06:39 UTCGHSA enrichment
  6. 2026-09-15 03:12 UTCEPSS rescore
  7. 2026-09-11 14:53 UTCEPSS rescore
  8. 2026-09-11 09:53 UTCOSV refresh
  9. 2026-09-11 09:37 UTCEPSS rescore
  10. 2026-09-08 22:01 UTCEPSS rescore
  11. 2026-09-07 16:01 UTCEPSS rescore
  12. 2026-09-06 13:47 UTCEPSS rescore
  13. 2026-09-05 15:31 UTCEPSS rescore
  14. 2026-09-04 05:07 UTCEPSS rescore
  15. 2026-09-02 14:12 UTCEPSS rescore
  16. 2026-09-01 13:54 UTCEPSS rescore
  17. 2026-09-01 04:40 UTCEPSS rescore
  18. 2026-08-30 19:17 UTCEPSS rescore
  19. 2026-08-30 01:22 UTCEPSS rescore
  20. 2026-08-28 21:42 UTCEPSS rescore
  21. 2026-08-26 14:47 UTCEPSS rescore
  22. 2026-08-25 13:49 UTCEPSS rescore
  23. 2026-08-23 17:57 UTCEG score recompute
  24. 2026-08-23 17:57 UTCVendor advisory
  25. 2026-08-23 17:57 UTCGHSA enrichment
Show 75 more
  1. 2026-08-23 00:19 UTCEPSS rescore
  2. 2026-08-21 23:49 UTCEPSS rescore
  3. 2026-08-20 22:56 UTCEPSS rescore
  4. 2026-08-20 21:33 UTCEG score recompute
  5. 2026-08-20 21:33 UTCVendor advisory
  6. 2026-08-20 21:33 UTCGHSA enrichment
  7. 2026-08-19 17:04 UTCEPSS rescore
  8. 2026-08-18 13:49 UTCEPSS rescore
  9. 2026-08-18 13:49 UTCEPSS rescore
  10. 2026-08-17 13:47 UTCEPSS rescore
  11. 2026-08-17 10:44 UTCEG score recompute
  12. 2026-08-17 10:44 UTCVendor advisory
  13. 2026-08-17 10:44 UTCGHSA enrichment
  14. 2026-08-16 14:56 UTCEPSS rescore
  15. 2026-08-16 14:56 UTCEPSS rescore
  16. 2026-08-16 04:08 UTCEG score recompute
  17. 2026-08-16 04:08 UTCVendor advisory
  18. 2026-08-16 04:08 UTCGHSA enrichment
  19. 2026-08-16 02:15 UTCEPSS rescore
  20. 2026-08-15 01:31 UTCEPSS rescore
  21. 2026-08-15 00:37 UTCVendor advisory
  22. 2026-08-15 00:37 UTCGHSA enrichment
  23. 2026-08-14 02:36 UTCEG score recompute
  24. 2026-08-14 02:36 UTCVendor advisory
  25. 2026-08-14 02:36 UTCGHSA enrichment
  26. 2026-08-13 22:00 UTCEPSS rescore
  27. 2026-08-12 21:17 UTCEG score recompute
  28. 2026-08-12 21:17 UTCVendor advisory
  29. 2026-08-12 21:17 UTCGHSA enrichment
  30. 2026-08-12 13:51 UTCEPSS rescore
  31. 2026-08-11 23:00 UTCEG score recompute
  32. 2026-08-11 23:00 UTCVendor advisory
  33. 2026-08-11 23:00 UTCGHSA enrichment
  34. 2026-08-11 00:59 UTCEG score recompute
  35. 2026-08-11 00:59 UTCVendor advisory
  36. 2026-08-11 00:59 UTCGHSA enrichment
  37. 2026-08-11 00:00 UTCEPSS rescore
  38. 2026-08-09 23:59 UTCEG score recompute
  39. 2026-08-09 23:59 UTCVendor advisory
  40. 2026-08-09 23:59 UTCGHSA enrichment
  41. 2026-08-09 13:47 UTCEPSS rescore
  42. 2026-08-09 01:58 UTCEG score recompute
  43. 2026-08-09 01:58 UTCVendor advisory
  44. 2026-08-09 01:58 UTCGHSA enrichment
  45. 2026-08-08 16:37 UTCEPSS rescore
  46. 2026-08-07 17:45 UTCEG score recompute
  47. 2026-08-07 17:45 UTCVendor advisory
  48. 2026-08-07 17:45 UTCGHSA enrichment
  49. 2026-08-06 19:44 UTCEG score recompute
  50. 2026-08-06 19:44 UTCVendor advisory
  51. 2026-08-06 19:44 UTCGHSA enrichment
  52. 2026-08-06 13:47 UTCEPSS rescore
  53. 2026-08-05 21:43 UTCEG score recompute
  54. 2026-08-05 21:43 UTCVendor advisory
  55. 2026-08-05 21:43 UTCGHSA enrichment
  56. 2026-08-05 19:17 UTCEPSS rescore
  57. 2026-08-05 19:17 UTCEPSS rescore
  58. 2026-08-04 15:10 UTCEPSS rescore
  59. 2026-08-04 10:39 UTCEPSS rescore
  60. 2026-08-03 19:11 UTCEG score recompute
  61. 2026-08-03 19:11 UTCVendor advisory
  62. 2026-08-03 19:11 UTCGHSA enrichment
  63. 2026-08-03 10:36 UTCEPSS rescore
  64. 2026-08-02 19:15 UTCEG score recompute
  65. 2026-08-02 19:15 UTCVendor advisory
  66. 2026-08-02 19:15 UTCGHSA enrichment
  67. 2026-08-02 02:27 UTCEPSS rescore
  68. 2026-08-01 21:14 UTCEG score recompute
  69. 2026-08-01 21:14 UTCVendor advisory
  70. 2026-08-01 21:14 UTCGHSA enrichment
  71. 2026-08-01 04:16 UTCEPSS rescore
  72. 2026-07-30 16:28 UTCEPSS rescore
  73. 2026-07-30 01:30 UTCEPSS rescore
  74. 2026-07-28 15:37 UTCEPSS rescore
  75. 2026-07-27 14:14 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-6253?
CVE-2026-6253 is a medium vulnerability published on May 13, 2026. curl might erroneously pass on credentials for a first proxy to a second proxy. This can happen when the following conditions are true: 1. curl is setup to use specific different proxies for different URL schemes 2. the first proxy needs credentials 3. the second proxy uses no credentials 4. while…
When was CVE-2026-6253 disclosed?
CVE-2026-6253 was first published in the National Vulnerability Database on May 13, 2026, with the most recent update on September 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-6253 actively exploited?
CVE-2026-6253 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 48.1% of all scored CVEs.
What is the CVSS score of CVE-2026-6253?
CVE-2026-6253 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2026-6253?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-6253, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-6253

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