CVE-2026-41263
Traefik: BasicAuth middleware: timing side-channel vulnerability
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a timing side-channel vulnerability in Traefik's BasicAuth middleware that allows an attacker to enumerate valid usernames through response-time differences. The variable intended to hold a constant-time fallback secret always resolves to an empty string, causing the constant-time comparison to short-circuit in microseconds rather than performing a full bcrypt evaluation. This restores the original timing oracle and makes it possible to distinguish existing users from non-existing ones by measuring authentication response times. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 4.0 | Medium6.3 | CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N |
| NVDNVD · Analyzed | 4.0 | Medium6.3 | CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.37% · top 69% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.3.
Weakness
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/traefik/traefikGHSA-6x2q-h3cr-8j2h (opens in a new tab)
- Gogithub.com/traefik/traefik/v2GHSA-6x2q-h3cr-8j2h (opens in a new tab)
- Gogithub.com/traefik/traefik/v3GHSA-6x2q-h3cr-8j2h (opens in a new tab)
References (4)
- https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h (opens in a new tab)x_refsource_CONFIRM
- https://github.com/traefik/traefik/releases/tag/v2.11.43 (opens in a new tab)x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v3.6.14 (opens in a new tab)x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-6x2q-h3cr-8j2h (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-41263)Record last updated .