Stack overwrite via malformed Digest nonce padding
Published Jun 10, 2021 · Updated Aug 4, 2024
Stack-based buffer overflow in mod_auth_digest in Apache HTTP Server 2.4.0 through 2.4.46 allows remote attackers to overwrite one stack byte. The check_nonce function validates only the nonce length before decoding its Base64-encoded time field, so malformed padding writes a terminating NUL past the stack buffer. Digest authentication must be enabled and the crafted nonce accepted; Apache reports no successful exploitation and limits the overwrite to one zero byte.
Summary
What happened
Stack-based buffer overflow in mod_auth_digest in Apache HTTP Server 2.4.0 through 2.4.46 allows remote attackers to overwrite one stack byte. The check_nonce function validates only the nonce length before decoding its Base64-encoded time field, so malformed padding writes a terminating NUL past the stack buffer. Digest authentication must be enabled and the crafted nonce accepted; Apache reports no successful exploitation and limits the overwrite to one zero byte.
The record
- CVE
- CVE-2020-35452
- Published
- Jun 10, 2021
- Updated
- Aug 4, 2024
- Vendor
- The Apache Software Foundation
- Product
- Apache HTTP Server
- Classifications
- T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 10, 2021CVE publishedPublication date reported by the CVE source.
- Aug 4, 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.
- Affected versionversion=2.4.0
- Affected versionversion=2.4.1
- Affected versionversion=2.4.10
- Affected versionversion=2.4.12
- Affected versionversion=2.4.16
- Affected versionversion=2.4.17
- Affected versionversion=2.4.18
- Affected versionversion=2.4.2
- Affected versionversion=2.4.20
- Affected versionversion=2.4.23
- Affected versionversion=2.4.25
- Affected versionversion=2.4.26
- Affected versionversion=2.4.27
- Affected versionversion=2.4.28
- Affected versionversion=2.4.29
- Affected versionversion=2.4.3
- Affected versionversion=2.4.33
- Affected versionversion=2.4.34
- Affected versionversion=2.4.35
- Affected versionversion=2.4.37
- Affected versionversion=2.4.38
- Affected versionversion=2.4.39
- Affected versionversion=2.4.4
- Affected versionversion=2.4.41
- Affected versionversion=2.4.43
- Affected versionversion=2.4.46
- Affected versionversion=2.4.6
- Affected versionversion=2.4.7
- Affected versionversion=2.4.9
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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