CVE-2021-22948Network attack vector

Account takeover via predictable session identifiers

Published Sep 23, 2021 · Updated Aug 3, 2024

Weak session ID generation in Revive Adserver before 5.3.0 allows remote attackers to take over accounts by brute-forcing identifiers. The phpAds_SessionGenerateId function in www/admin/lib-sessions.inc.php hashes output from PHP's predictable uniqid function instead of using a cryptographically secure generator. No authentication is required to guess an active identifier, but exploitation depends on conditions that make a specific user's session identifier predictable; successful reuse grants that user's account access.

CVSS severity6.5
Medium
EPSS probability2.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Weak session ID generation in Revive Adserver before 5.3.0 allows remote attackers to take over accounts by brute-forcing identifiers. The phpAds_SessionGenerateId function in www/admin/lib-sessions.inc.php hashes output from PHP's predictable uniqid function instead of using a cryptographically secure generator. No authentication is required to guess an active identifier, but exploitation depends on conditions that make a specific user's session identifier predictable; successful reuse grants that user's account access.

The record

CVE
CVE-2021-22948
Published
Sep 23, 2021
Updated
Aug 3, 2024
Vendor
Revive Adserver Project
Product
Revive Adserver
Classifications
CWE-327, CWE-338, T1550.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=Fixed version v5.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Revive Adserver Project · Revive Adserverversion=Fixed version v5.3.0

Published CVSS scores

7.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:P/I:N/A:N
6.5Revive AdserverCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/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.

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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
CWE-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
T1550.004Use Alternate Authentication Material: Web Session Cookie

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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