CVE-2026-6276

HIGHNVD 7.57.5
EchelonGraph scoreMEDIUM confidence

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

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-05-13. NVD baseline CVSS 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Elevated
7.5EG
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: 0.3%CVSS: 7.5Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

Using libcurl, when a custom Host: header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom Host: header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
65
EG Risk 65/100

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 (value × EchelonGraph’s weight)
Severity75% × 45%
The EG Score, 7.5 of 10.
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 or medium mission impact; Attend at high (mission-essential systems).
Exploitation public PoC (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 available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
26th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

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 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

May 13, 2026

Last Modified

September 15, 2026

Advisory Details (4)

Auto-updated May 13, 2026
Patch available.
Web page

HackerOne

https://hackerone.com/reports/3671818
Web page

oss-security - [ADVISORY] curl: CVE-2026-6276: stale custom cookie host causes cookie leak

http://www.openwall.com/lists/oss-security/2026/04/29/13
Web page
https://curl.se/docs/CVE-2026-6276.json
Web page

curl - stale custom cookie host causes cookie leak - CVE-2026-6276

https://curl.se/docs/CVE-2026-6276.html

Vendor Advisories for CVE-2026-6276(3)

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

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibcurl4t64 (8.18.0-1ubuntu2.1) @ resolute2026-09-15ubuntu
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 rangeFix by version rangeDependents
curl—
  • 7.71.0 up to 8.20.0-r0: fixed in 8.20.0-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
curl—
  • 7.71.0 up to 8.20.0-r0: fixed in 8.20.0-r0
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
curl7.74.0-1.3 ... 8.9.1-2~bpo12+1 (219 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
curl7.88.1-10 ... 8.9.1-2~bpo12+1 (184 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
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+deb13u3
  • every version up to 8.14.1-2+deb13u4: fixed in 8.14.1-2+deb13u4
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
curl8.14.1-2 ... 8.20.0~rc2-1+exp1 (47 versions)
  • every version up to 8.20.0~rc3-1: fixed in 8.20.0~rc3-1
—

Weakness Classification(2)

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 11× in last 7d / 33× 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 98 of 310 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. 2 repeat rows among the latest 100 are merged into the row they repeat. The 212 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  2. 2026-10-12 15:49 UTCEG score recompute
  3. 2026-10-11 19:33 UTCEG score recompute
  4. 2026-10-11 16:48 UTCEG score recompute
  5. 2026-10-11 14:10 UTCEG score recompute
  6. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  7. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  8. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  9. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  10. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  11. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  12. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  13. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  14. 2026-10-04 22:48 UTCOSV refresh
  15. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  16. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  17. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  18. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  19. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  20. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  21. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  22. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  23. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  24. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  25. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
Show 73 more
  1. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  2. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  3. 2026-09-15 07:26 UTCVendor advisory
  4. 2026-09-15 07:26 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  5. 2026-09-15 06:39 UTCEG score recompute
  6. 2026-09-15 06:39 UTCVendor advisory
  7. 2026-09-15 06:39 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  8. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  9. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  10. 2026-09-11 09:53 UTCOSV refresh
  11. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  12. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  13. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  14. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  15. 2026-09-05 15:31 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  16. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  17. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  18. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  19. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  20. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  21. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  22. 2026-08-28 21:42 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  23. 2026-08-26 14:47 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  24. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  25. 2026-08-23 17:57 UTCEG score recompute
  26. 2026-08-23 17:57 UTCVendor advisory
  27. 2026-08-23 17:57 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  28. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  29. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  30. 2026-08-20 22:56 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  31. 2026-08-20 21:33 UTCEG score recompute
  32. 2026-08-20 21:33 UTCVendor advisory
  33. 2026-08-20 21:33 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  34. 2026-08-19 17:04 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  35. 2026-08-18 13:49 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  36. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  37. 2026-08-17 10:44 UTCEG score recompute
  38. 2026-08-17 10:44 UTCVendor advisory
  39. 2026-08-17 10:44 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  40. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  41. 2026-08-16 04:08 UTCEG score recompute
  42. 2026-08-16 04:08 UTCVendor advisory
  43. 2026-08-16 04:08 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  44. 2026-08-16 02:15 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
  45. 2026-08-15 02:07 UTCEG score recompute
  46. 2026-08-15 02:07 UTCVendor advisory
  47. 2026-08-15 02:07 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  48. 2026-08-15 01:31 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  49. 2026-08-14 14:22 UTCVendor advisory
  50. 2026-08-14 14:22 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  51. 2026-08-14 02:36 UTCEG score recompute
  52. 2026-08-14 02:36 UTCVendor advisory
  53. 2026-08-14 02:36 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  54. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  55. 2026-08-13 03:39 UTCVendor advisory
  56. 2026-08-13 03:39 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  57. 2026-08-12 15:54 UTCEG score recompute
  58. 2026-08-12 15:54 UTCVendor advisory
  59. 2026-08-12 15:54 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  60. 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  61. 2026-08-11 15:30 UTCEG score recompute
  62. 2026-08-11 15:30 UTCVendor advisory
  63. 2026-08-11 15:30 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  64. 2026-08-11 01:01 UTCEG score recompute
  65. 2026-08-11 01:01 UTCVendor advisory
  66. 2026-08-11 01:01 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  67. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  68. 2026-08-10 13:15 UTCVendor advisory
  69. 2026-08-10 13:15 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  70. 2026-08-10 01:29 UTCEG score recompute
  71. 2026-08-10 01:29 UTCVendor advisory
  72. 2026-08-10 01:29 UTCGHSA enrichmentGHSA-2jc6-hc33-hv48 · GitHub severity HIGH · GitHub CVSS 7.5
  73. 2026-08-09 13:47 UTCEPSS rescoreEPSS 0.3% · 21st percentile

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Frequently asked(5)

What is CVE-2026-6276?
CVE-2026-6276 is a high-severity vulnerability; its CVE record was published on May 13, 2026. Using libcurl, when a custom Host: header is first set for an HTTP request and a second request is subsequently done using the same easy handle but without the custom Host: header set, the second request would use stale information and pass on cookies meant for the first host in the second request.…
When was the CVE record for CVE-2026-6276 published?
The CVE record for CVE-2026-6276 was published on May 13, 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 September 15, 2026; the record at its source may have been updated since.
Is CVE-2026-6276 actively exploited?
CVE-2026-6276 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (26th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-6276?
CVE-2026-6276 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-6276?
A fix for CVE-2026-6276 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-6276 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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