Caddy: rewrite placeholder re-expansion, unbounded body buffer DoS, and fileHidden case-sensitivity bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L

EPSS

• CVE-2026-77281: 0.49% estimated exploitation activity in the next 30 days; percentile 42.26 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
• CVE-2026-92284: 0.39% estimated exploitation activity in the next 30 days; percentile 32.95 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
• CVE-2026-92700: 0.41% estimated exploitation activity in the next 30 days; percentile 35.47 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Caddy v2.11.3 — Three vulnerabilities in handler/placeholder layer Tested against: caddy:2.11.3 (official Docker image, SHA verified at runtime) Reproduction environment: Docker Desktop 4.73.1 / Engine 29.4.3 on Windows 10 host, isolated containers, no network egress required for any of the exploits This advisory bundles three independent issues discovered together during a source review of the placeholder/replacer layer. Each issue has been reproduced end-to-end against the unmodified caddy:2.11.3 image with the minimal Caddyfile that the documentation suggests for the affected feature. --- Issue 1: Rewrite handler — placeholder double-expansion enables env var / file disclosure File: modules/caddyhttp/rewrite/rewrite.go:215-249 and buildQueryString at 327 Class: CWE-94 (Code Injection), same bug class as CVE-2026-30852 (varsregexp) Severity: Low (requires operator config with trailing ? in rewrite URI) Root cause When the operator's rewrite URI template: 1. Contains a placeholder…

Published by the source

18 Sep 2026, 13:09 UTC

Last modified by the source

1 Oct 2026, 20:55 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-j8px-rmrx-76h9

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6512

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-j8px-rmrx-76h9

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# Patch Next advisory brief: CVE-2026-77281

Advisory: Caddy: rewrite placeholder re-expansion, unbounded body buffer DoS, and fileHidden case-sensitivity bypass
IDs: CVE-2026-77281, GHSA-j8px-rmrx-76h9
Record: https://patchnext.com/advisories/cve-2026-77281 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/caddyserver/caddy/v2 2.11.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/caddyserver/caddy/v2: affected <= 2.11.3; fixed in 2.11.4

## Suggested inspection (read-only)
- Go github.com/caddyserver/caddy/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/caddyserver/caddy/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-j8px-rmrx-76h9 (OSV record GHSA-j8px-rmrx-76h9 lists affected ranges: Go github.com/caddyserver/caddy/v2 >=0 <2.11.4 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6512 (OSV record GO-2026-6512 lists affected ranges: Go github.com/caddyserver/caddy/v2 >=0 <2.11.4 (fixed))
- Verified: https://github.com/advisories/GHSA-j8px-rmrx-76h9 (GitHub-reviewed advisory GHSA-j8px-rmrx-76h9 lists affected ranges: Go github.com/caddyserver/caddy/v2 >=0 <=2.11.3)

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