CVE-2023-43804Network attack vector

Cookie disclosure via cross-origin redirect forwarding

Published Oct 4, 2023 · Updated Nov 3, 2025

Information disclosure in urllib3 before 1.26.17 and 2.0.0 through 2.0.5 allows remote attackers to obtain Cookie headers via redirects. Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT omits Cookie, so PoolManager forwards a caller-supplied header when an automatic redirect changes hosts. Exposure requires an enabled redirect, a supplied Cookie header, and either HTTP or an origin that redirects to an attacker-controlled origin.

CVSS severity5.9
Medium
EPSS probability1.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in urllib3 before 1.26.17 and 2.0.0 through 2.0.5 allows remote attackers to obtain Cookie headers via redirects. Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT omits Cookie, so PoolManager forwards a caller-supplied header when an automatic redirect changes hosts. Exposure requires an enabled redirect, a supplied Cookie header, and either HTTP or an origin that redirects to an attacker-controlled origin.

The record

CVE
CVE-2023-43804
Published
Oct 4, 2023
Updated
Nov 3, 2025
Vendor
urllib3
Product
urllib3
Classifications
CWE-200, T1539
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Oct 4, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record 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=< 1.26.17
  2. Affected versionversion=>= 2.0.0, < 2.0.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

urllib3 · urllib3version=< 1.26.17; version=>= 2.0.0, < 2.0.6

Published CVSS scores

8.1NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
5.9GitHubCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1539Steal Web Session Cookie

Public exploit references

No public exploit references are available in this record.

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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