CVE-2021-46900Network attack vector

Cross-site scripting via predictable archive tags

Published Dec 31, 2023 · Updated Apr 17, 2025

Cross-site scripting in Sympa before 6.2.62 allows remote attackers to execute script through crafted messages rendered in web archives. Sympa::Archive::_get_tag derives randomized archive tags from the site-wide cookie setting without requiring a unique, unpredictable secret. A missing cookie disables this protection, while a weak value permits brute-force prediction and exposes archive viewers to injected script.

CVSS severity7.5
High
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Sympa before 6.2.62 allows remote attackers to execute script through crafted messages rendered in web archives. Sympa::Archive::_get_tag derives randomized archive tags from the site-wide cookie setting without requiring a unique, unpredictable secret. A missing cookie disables this protection, while a weak value permits brute-force prediction and exposes archive viewers to injected script.

The record

CVE
CVE-2021-46900
Published
Dec 31, 2023
Updated
Apr 17, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-327, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 31, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 17, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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 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 exploitUnconfirmed

Weakness, pattern, technique

CWE-327Use of a Broken or Risky Cryptographic Algorithm
T1059.007JavaScript/JScript

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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