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.
CVE-2026-77281
MEDIUMPre-NVD 6.56.5Trending — 3 sources updated this week
EchelonGraph scoreLOW confidence
This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). 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: secondary
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 6.5
- EG Score
- 6.5(low)
- EG Risk
- 44(Track)EG Risk 44/100SSVC: 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 computedSeverity65% × 45%Exploitation0% × 40%Automatability100% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 30%
- KEV
- Not listed
Published
September 17, 2026
Last Modified
September 18, 2026
Advisory Details (4)
Auto-updated Sep 17, 2026🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_pr, github_release.
github Patch Available🟡 PoC Available
Three vulnerabilities in Caddy v2.11.3: rewrite placeholder re-expansion, unbounded body buffer DoS, and fileHidden case-sensitivity bypass · Advisory · caddyserver/caddy · GitHub
https://github.com/caddyserver/caddy/security/advisories/GHSA-j8px-rmrx-76h9github_release Patch Available
v2.11.4
Patch available: caddyserver/caddy v2.11.4
https://github.com/caddyserver/caddy/releases/tag/v2.11.4github_pr
rewrite: prevent placeholder re-expansion in injected query
Fix merged in caddyserver/caddy PR #7761 on 2026-05-26 — awaiting tagged release
https://github.com/caddyserver/caddy/pull/7761github_commit
commit 176b043b0104 (caddyserver/caddy)
Fix landed in caddyserver/caddy commit 176b043b0104 — awaiting tagged release
https://github.com/caddyserver/caddy/commit/176b043b0104cee3f894023cd5a598ac29e404bbVendor Advisories for CVE-2026-77281(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
Go(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| github.com/caddyserver/caddy/v2 | — | 2.11.4 | — |
Weakness Classification(3)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 6× in last 7d / 6× 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.
- 2026-09-18 19:28 UTCEPSS rescore
- 2026-09-18 15:26 UTCEG score recompute
- 2026-09-18 14:54 UTCEG score recompute
- 2026-09-17 21:20 UTCEG score recompute
- 2026-09-17 21:14 UTCEG score recompute
- 2026-09-17 21:14 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Same CWE
10 shownCWE-94 · CWE-178
Frequently asked(5)
What is CVE-2026-77281?
CVE-2026-77281 is a medium vulnerability published on September 17, 2026. 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…
When was CVE-2026-77281 disclosed?
CVE-2026-77281 was first published in the National Vulnerability Database on September 17, 2026, with the most recent update on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-77281 actively exploited?
CVE-2026-77281 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 70.2% of all scored CVEs.
What is the CVSS score of CVE-2026-77281?
CVE-2026-77281 has a CVSS v3 base score of 6.5 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-77281?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-77281, 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
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-77281
Is Your Infrastructure Affected by CVE-2026-77281?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.