CVE-2026-30851: caddyserver caddy Improper Authentication
CVSS: 8.8v3.1HighAnalyzed
AliasesUBUNTU-CVE-2026-30851GHSA-7r4p-vjf4-gxv4GO-2026-4639
Published 07-03-2026Last modified 09-03-2026
Vulnerability summary
CVE-2026-30851 is a high (CVSS 8.8) Improper Authentication vulnerability in caddyserver caddy. EPSS estimates a 0.36% chance of exploitation in the next 30 days, higher than 28.4% of scored vulnerabilities. 1 public exploit is recorded.
CVSS score
8.8/10
010
High · v3.1 (NVD)EPSS score
0.36%
0%100%
Low · +0.11 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits1github
Advisory lineage
Upstream 0 · Downstream 2 · Related 2Timeline
- 07-03-2026PublishedVulnerability first disclosed.
- 09-03-2026Last modifiedVulnerability information updated.
Description
Caddy is an extensible server platform that uses TLS by default. From version 2.10.0 to before version 2.11.2, forward_auth copy_headers does not strip client-supplied headers, allowing identity injection and privilege escalation. This issue has been patched in version 2.11.2.
CVSS metrics
4 scores · 4 sources · 1 versionHigh 8.8Preferred score · NVD (NIST)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HSources4 sources · 8.1–8.8
- CVE.orgCNA8.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:NDiffers
- OSV · UbuntuEcosystem advisory · calculated8.8HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · GoEcosystem advisory · calculated8.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:NDiffers
EPSS trend
Probability
0.36%
Chance of exploitation in the next 30 days
Percentile
28%
Versus all other CVEs
30-day change
+0.11 pp
From 0.25% on 20-09-2026
20-09-202620-10-2026
EPSS score0.36%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundCaddy
Maturity: poc
Weaknesses
CWE · root cause- CWE-287Improper AuthenticationWhen an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
- CWE-345Insufficient Verification of Data AuthenticityThe product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.
Affected systems
Caddyserver1 product
- caddy≥ 2.10.0, < 2.11.2
Github.com/caddyserver/caddy1 product
- v2≥ 2.10.0, < 2.11.2
Github.com/caddyserver/caddy/v2/modules/caddyhttp1 product
- reverseproxy≥ 2.10.0, < 2.11.2
Ubuntu1 product
- caddyAll versions (No fix recorded)
4 vendors · 4 products
References
8 links- github.com/caddyserver/caddy/security/advisories/GHSA-7r4p-vjf4-gxv4X Refsource CONFIRMREPORTWEBAdvisoryExploitMitigationPatchVendor Advisory
- github.com/caddyserver/caddyPACKAGE