CVE-2026-40594Public exploitNetwork attack vector

Session disruption via spoofed proxy header race

Published Apr 21, 2026 · Updated Apr 21, 2026

Origin validation error in pyLoad before 0.5.0b3.dev98 allows remote attackers to disrupt sessions via spoofed proxy headers. The set_session_cookie_secure handler trusts X-Forwarded-Proto from any request and rewrites the global SESSION_COOKIE_SECURE setting during concurrent processing. The unauthenticated race breaks sessions on default plain HTTP deployments; direct backend access behind a TLS proxy can also strip Secure flags.

CVSS severity4.8
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Origin validation error in pyLoad before 0.5.0b3.dev98 allows remote attackers to disrupt sessions via spoofed proxy headers. The set_session_cookie_secure handler trusts X-Forwarded-Proto from any request and rewrites the global SESSION_COOKIE_SECURE setting during concurrent processing. The unauthenticated race breaks sessions on default plain HTTP deployments; direct backend access behind a TLS proxy can also strip Secure flags.

The record

CVE
CVE-2026-40594
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
pyLoad
Product
pyLoad
Classifications
CWE-346, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.5.0b3.dev98

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

pyLoad · pyLoadversion=< 0.5.0b3.dev98

Published CVSS scores

4.8GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-346Origin Validation Error
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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