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Fencer Vulns
medium 6.5

CVE-2026-77281 json

Caddy: rewrite placeholder re-expansion

published 2026-09-17 52 d ago modified 2026-10-03 37 d ago also CVE-2026-92284 , CVE-2026-92700 , GHSA-j8px-rmrx-76h9 , GO-2026-6512 , EUVD-2026-82474

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

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.

Patch / fix

  • go github.com/caddyserver/caddy/v2 2.11.4
  • caddy Debian 12 2.6.2-5+deb12u1
  • caddy Debian 14 2.11.4-1

debian advisories DEBIAN-CVE-2026-77281

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
51 d ago

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
GitHub 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L

Affected packages

ecosystem package affected fixed in
go github.com/caddyserver/caddy/v2
<2.11.4
2.11.4

Affected products

  • caddyserver caddy

Classification

Weakness
  • CWE-94 Improper Control of Generation of Code
  • CWE-178 Improper Handling of Case Sensitivity
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.