CVE-2026-86409

HIGHPre-NVD 8.18.1
EchelonGraph scoreMEDIUM confidence

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

This high-severity CVE scores 8.1 under CISA-ADP (Vulnrichment) CVSS v3.1 (NVD's own analysis pending). EPSS exploit probability: 0.3% (24th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from CISA-ADP (Vulnrichment) CVSS v3.1
Sources: CISA-ADP (Vulnrichment) CVSS v3.1, EPSS
Trending — 5 sources updated this weekElevated

Also known asEUVD-2026-105274 (ENISA EUVD) · GHSA-57hx-469r-xq3r (GitHub Security Advisories)Source: ENISA EUVD

8.1EG
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: 8.1Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

Setting CURLOPT_AWS_SIGV4 to NULL but does not disable SigV4 authentication, contrary to expectations and documentation. A subsequent transfer on the same handle still sends an Authorization: AWS4-HMAC-SHA256 header to whatever URL isset next, leaking state information.

CVSS v3
8.1
EG Score
8.1HIGHmedium confidence
EG Risk
52
EG 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)
Severity81% × 45%
Impact severity (EG Severity): CVSS 8.1 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.
Automatability0% × 15%
CISA's SSVC Automatable value: no (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 no (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
0.3%
EPSS %ILE
24th
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 (8.1): severity, escalated by confirmed exploitation. This CVE's 8.1 is its impact severity (EG Severity), not escalated.

EG Severity
8.1 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.CISA-ADP (Vulnrichment) CVSS v3.1 · CVSS v3.1
EG Likelihood
0.3% 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: 14 days if the affected system is publicly exposed; Fix on system upgrade 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 no (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)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (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

October 20, 2026

Last Modified

October 29, 2026

Advisory Details (3)

Auto-updated Oct 29, 2026
Patch available.
Web page

HackerOne

https://hackerone.com/reports/3973135
Web page

curl - stale SigV4 headers sent unintended - CVE-2026-86409

https://curl.se/docs/CVE-2026-86409.html
Web page
https://curl.se/docs/CVE-2026-86409.json

Vendor Advisories for CVE-2026-86409(2)

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

Patch Availability(4)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibcurl4t64 (8.20.0-2ubuntu11.1) @ stonking2026-10-29ubuntu
ubuntulibcurl4t64 (8.18.0-1ubuntu2.8) @ resolute2026-10-29ubuntu
ubuntulibcurl4-openssl-dev (7.47.0-1ubuntu2.19+esm21) @ xenial2026-10-29ubuntu
redhatcurl-main-8.23.0-0.1.hum12026-10-14redhat

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.

Weakness Classification(1)

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

Additional Vendor Advisories

(3)

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 15× in last 7d / 25× 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.

  1. 2026-10-29 19:26 UTCEG score recompute
  2. 2026-10-29 19:26 UTCVendor advisory
  3. 2026-10-29 19:26 UTCGHSA enrichmentGHSA-57hx-469r-xq3r
  4. 2026-10-29 18:47 UTCEG score recomputeFirst assessed: 8.1 HIGH
  5. 2026-10-29 18:47 UTCVendor advisory
  6. 2026-10-29 18:47 UTCGHSA enrichmentGHSA-57hx-469r-xq3r
  7. 2026-10-29 18:46 UTCMITRE cvelistV5CVSS v3 → 8.1 · severity → HIGH
  8. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  9. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  10. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 24th percentile
  11. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  12. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  13. 2026-10-25 13:54 UTCEG score recompute
  14. 2026-10-24 16:34 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  15. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  16. 2026-10-22 17:31 UTCEG score recompute
  17. 2026-10-22 17:31 UTCVendor advisory
  18. 2026-10-22 17:31 UTCGHSA enrichmentGHSA-57hx-469r-xq3r
  19. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  20. 2026-10-21 16:34 UTCEPSS rescoreEPSS 0.2% · 15th percentile
  21. 2026-10-20 20:26 UTCVendor advisory
  22. 2026-10-20 20:25 UTCNVD update
  23. 2026-10-20 20:05 UTCEG score recompute
  24. 2026-10-20 20:05 UTCVendor advisory
  25. 2026-10-20 20:01 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-86409?
CVE-2026-86409 is a high-severity vulnerability; its CVE record was published on October 20, 2026. Setting CURLOPTAWSSIGV4 to NULL but does not disable SigV4 authentication, contrary to expectations and documentation. A subsequent transfer on the same handle still sends an Authorization: AWS4-HMAC-SHA256 header to whatever URL isset next, leaking state information.
When was the CVE record for CVE-2026-86409 published?
The CVE record for CVE-2026-86409 was published on October 20, 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 29, 2026; the record at its source may have been updated since.
Is CVE-2026-86409 actively exploited?
CVE-2026-86409 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (24th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-86409?
CVE-2026-86409 has a CVSS v3.1 base score of 8.1 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-86409?
A fix for CVE-2026-86409 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-86409 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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