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01 Record

CVE-2026-52845

Caddy: FastCGI header normalization bypass in `forward_auth copy_headers`

HighPUBLISHEDCNA: GitHub_M
CNA base score8.1 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

02 Description

Caddy: FastCGI header normalization bypass in `forward_auth copy_headers`

03 Exploitation and scoring

Exploitation
Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.
SSVC decision
  • ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
  • AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
  • Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.44% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 38.4% of scored records. A rank, not a probability.
NVD base score
8.1 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
NVD analysis status
Modified. NVD last modified this record on 2026-10-25.
Red Hat severity
Important. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-06-23 17:52Z4 MO AGO
Last updated
2026-07-15 00:46Z3 MO AGO
Reserved
2026-06-08
Assigning CNA
GitHub_M
Record state
PUBLISHED
Severity
High (CVSS 8.1)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Weaknesses
  • CWE-287Improper AuthenticationClass
  • CWE-290Authentication Bypass by SpoofingBase
  • CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')Base
Data version
5.2
Document digest
dfda9d1c4705ef6460158cca66938832a5af9784f210412341a13a7c570fba8f

05 Affected products

VendorProductVersionsPlatforms
caddyservercaddy< 2.11.4—

06 References

07 Fixed in

Debian 12

  • caddy
    Fixed in 2.6.2-5+deb12u1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

  • caddy
    Fixed in 2.6.2-12+deb13u1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

  • caddy
    Fixed in 2.11.4-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 25.10

  • caddy
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 26.10

  • caddy
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 24.04 LTS

  • caddy
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 26.04 LTS

  • caddy
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.