TI-2026-53958 Aliases CVE-2026-77281 GHSA-j8px-rmrx-76h9

Caddy: rewrite placeholder re-expansion

LOW 35CWE-178Published 2026-09-17 · Updated 2026-09-18

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service, Code execution
Confidentiality · integrity · availability: Low · None · Low
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-770 and CWE-94.

Summary

Caddy is an extensible server platform that uses TLS by default. In version 2.11.3 and earlier, three configuration-dependent weaknesses affect the handler and placeholder layer. In modules/caddyhttp/rewrite/rewrite.go, Rewrite.Rewrite() can pass attacker-controlled replacement bytes through buildQueryString for a second placeholder expansion when a rewrite URI ends with a literal question mark, allowing injected environment or request-variable placeholders to disclose data and, when the file provider is registered, allowing injected file placeholders to disclose readable files. The issue is fixed in version 2.11.4.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00491 42nd percentileScored 2026-11-07

Fix Fixed caddy (caddyserver): 2.11.4github.com/caddyserver/caddy/v2 (Go): 2.11.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
caddyserver	caddy	before 2.11.4	2.11.4	Patch available	CNA
—	github.com/caddyserver/caddy/v2 (Go)	before 2.11.4	2.11.4	Patch available	GHSA-j8px-rmrx-76h9

caddy Vendorcaddyserver Affected before 2.11.4 Fixed in 2.11.4 Patch available CNA
github.com/caddyserver/caddy/v2 (Go) Vendor— Affected before 2.11.4 Fixed in 2.11.4 Patch available GHSA-j8px-rmrx-76h9

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:caddyserver:caddy::::::::	—	—	caddyserver

cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:* Versions — — ·caddyserver

Remediation

Fix · CNA caddy (caddyserver) Fixed in 2.11.4
Fix · GHSA-j8px-rmrx-76h9 github.com/caddyserver/caddy/v2 (Go) Fixed in 2.11.4 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-77281
2026-10-03 Alias added: GHSA-j8px-rmrx-76h9

References

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-77281

Other 5

TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
TI-2026-21978 Improper input validation in caddyserver caddy CVSS 4.0HIGH 8.9
TI-2026-21974 Caddy's mTLS client authentication silently fails open when CA certificate file is missing or malformed CVSS 4.0HIGH 8.8
TI-2026-23680 Improper authentication in caddyserver caddy CVSS 3.1HIGH 8.8
TI-2026-21976 Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass CVSS 4.0HIGH 7.7
TI-2026-21975 Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass CVSS 4.0HIGH 7.7

See all 23 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences