Pre-auth memory corruption via undersized base64 buffer
Published Aug 4, 2026 · Updated Aug 4, 2026
Buffer overflow in OpenSIPS 3.4.0-beta through 3.6.5 and 4.0.0-beta allows remote attackers to corrupt memory via crafted SIP headers. The {s.b64encode} path checks only whether input fits its 65,536-byte transformation buffer, then writes the larger base64 output into that buffer and adjacent chain storage. Exploitation requires TCP delivery of an oversized header and a routing script that applies the transformation to attacker-controlled content, enabling corruption of later transformation values.
Summary
What happened
Buffer overflow in OpenSIPS 3.4.0-beta through 3.6.5 and 4.0.0-beta allows remote attackers to corrupt memory via crafted SIP headers. The {s.b64encode} path checks only whether input fits its 65,536-byte transformation buffer, then writes the larger base64 output into that buffer and adjacent chain storage. Exploitation requires TCP delivery of an oversized header and a routing script that applies the transformation to attacker-controlled content, enabling corruption of later transformation values.
The record
- CVE
- CVE-2026-45100
- Published
- Aug 4, 2026
- Updated
- Aug 4, 2026
- Vendor
- OpenSIPS
- Product
- OpenSIPS
- Classifications
- CWE-120, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 4, 2026CVE publishedPublication date reported by the CVE source.
- Aug 4, 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.
- Affected versionversion=>= 3.4.0-beta, < 3.6.6
- Affected versionversion=>= 4.0.0-beta, < 4.0.0-rc1
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- poc-b64encode-overflow.pyproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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