CVE-2026-15806

MEDIUMPre-NVD 6.06.0—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.0 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 69% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 4 sources updated this weekElevated
6.0EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.0Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

The HTTPPasswordMgr class in the urllib.request module, along with its subclasses HTTPPasswordMgrWithDefaultRealm and HTTPPasswordMgrWithPriorAuth, did not take the URL scheme into account when matching stored credentials against a requested URL. Credentials added for an https:// URL were also used for requests to the same host over http://, so an attacker able to redirect or downgrade a client to plain HTTP (for example, via an HTTPS-to-HTTP redirect or an on-path position) could capture credentials in cleartext. Credentials added for http:// URLs could likewise be sent over https://.

Credential matching is now scoped by URL scheme. Credentials registered with a URL that includes a scheme are only used for requests with the same scheme. Credentials registered with a bare authority (such as example.com or example.com:8080) continue to match any scheme, preserving compatibility with existing code, including proxy authentication.

Users who cannot upgrade immediately can mitigate by ensuring that applications never make plain http:// requests to hosts for which credentials are registered, for example by not following redirects to http:// URLs.

CVSS v3
6.0
EG Score
6.0(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
Severity60% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
31%
KEV
Not listed

Published

August 18, 2026

Last Modified

August 21, 2026

Advisory Details (3)

Auto-updated Aug 18, 2026
Upstream fix merged — awaiting tagged release. Sources: github_pr.
generic

Mailman 3 [CVE-2026-15806] urllib.request.HTTPPasswordMgr credentials for one URL scheme sent over another scheme - Security-announce - python.org

https://mail.python.org/archives/list/[email protected]/thread/3OKPE5S75KDNA7FY7AI3PL2MXM2X5RB3/
github_pr

gh-155694: Scope HTTPPasswordMgr credentials by URL scheme

Fix merged in python/cpython PR #155696 on 2026-08-17 — awaiting tagged release

https://github.com/python/cpython/pull/155696
generic

`HTTPPasswordMgr` can send saved HTTPS credentials via HTTP because of incorrect scheme matching · Issue #155694 · python/cpython · GitHub

https://github.com/python/cpython/issues/155694

Vendor Advisories for CVE-2026-15806(1)

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

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 18× in last 7d / 18× 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.

  1. 2026-08-21 01:30 UTCEG score recompute
  2. 2026-08-21 01:30 UTCGHSA enrichment
  3. 2026-08-21 00:31 UTCEG score recompute
  4. 2026-08-21 00:31 UTCGHSA enrichment
  5. 2026-08-21 00:15 UTCEG score recompute
  6. 2026-08-21 00:15 UTCGHSA enrichment
  7. 2026-08-20 22:55 UTCEPSS rescore
  8. 2026-08-20 01:22 UTCEG score recompute
  9. 2026-08-20 01:21 UTCGHSA enrichment
  10. 2026-08-20 00:28 UTCEG score recompute
  11. 2026-08-20 00:28 UTCGHSA enrichment
  12. 2026-08-19 18:20 UTCEG score recompute
  13. 2026-08-19 18:20 UTCGHSA enrichment
  14. 2026-08-19 17:03 UTCEPSS rescore
  15. 2026-08-18 19:24 UTCGHSA enrichment
  16. 2026-08-18 16:28 UTCEG score recompute
  17. 2026-08-18 15:59 UTCEG score recompute
  18. 2026-08-18 15:59 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-15806?
CVE-2026-15806 is a medium vulnerability published on August 18, 2026. The HTTPPasswordMgr class in the urllib.request module, along with its subclasses HTTPPasswordMgrWithDefaultRealm and HTTPPasswordMgrWithPriorAuth, did not take the URL scheme into account when matching stored credentials against a requested URL. Credentials added for an https:// URL were also used…
When was CVE-2026-15806 disclosed?
CVE-2026-15806 was first published in the National Vulnerability Database on August 18, 2026, with the most recent update on August 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-15806 actively exploited?
CVE-2026-15806 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 69.5% of all scored CVEs.
What is the CVSS score of CVE-2026-15806?
CVE-2026-15806 has a CVSS v3 base score of 6.0 (NVD).
How do I remediate CVE-2026-15806?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-15806, 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

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