Reported by 2 outlets
Exim Mail Server Hit by 4 Security Flaws Enabling SMTP Smuggling and Heap Corruption
Why this score
- Breadth
- 1.00 / 2.0 · 2 sources
- Authority
- 1.20 / 2.0 · best outlet weight
- Severity
- 0.50 / 5.0 · CVSS + content signals
- Velocity
- 0.00 / 2.0 · updates in 48h
- Pickup speed
- 0.60 / 0.6 · time to second source
- Recency
- × 0.00 temporal multiplier
- Community
- + 0.00 / 1.5 · reddit signal
- Score
- 0.0 / 10 = base × recency + community
Timeline
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original reporting
Exim Mail Server Hit by 4 Security Flaws Enabling SMTP Smuggling and Heap Corruption
gbhackers.com · 22d ago · September 21st, 2026
Exim maintainers have released version 4.100.1 to address four security vulnerabilities affecting the widely used mail transfer agent. This update resolves issues that could potentially enable SMTP smuggling and heap-memory corruption under certain configurations. The release, announced on September 18, fixes the following vulnerabilities: GCVE-25-2026-09-50-1, GCVE-25-2026-09-51-1, GCVE-25-2026-09-55-1, and GCVE-25-2026-09-56-1. Administrators using vulnerable installations of Exim […] The post Exim Mail Server Hit by 4 Security Flaws Enabling SMTP Smuggling and Heap Corruption appeared first on GBHackers Security | #1 Globally Trusted Cyber Security News Platform .
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update from cyberpress.org
Exim Mail Server Flaws Enable SMTP Smuggling, Heap Corruption and Data Leakage
cyberpress.org · 22d ago · September 21st, 2026
Exim has released version 4.100.1 to address four security vulnerabilities affecting its mail transfer agent , including SMTP smuggling, heap corruption, stack-data leakage, and a use-after-free condition. Two high-severity vulnerabilities affect Exim’s handling of Proxy Protocol traffic, while a medium-severity SMTP smuggling flaw impacts all Exim versions through 4.100. Exim Mail Server Flaws The most serious issue, GCVE-25-2026-09-50-1, is an out-of-bounds write and heap-corruption vulnerability in Proxy Protocol v1 handling. It affects Exim releases from version 4.83 through 4.100 when the server is built and configured to use Proxy Protocol. A remote attacker could trigger a read of approximately 230 bytes beyond a heap allocation and cause a single NUL-byte write immediately after the read range. Exploitation requires an upstream configured proxy to be buggy or compromised. Nevertheless, the flaw highlights the risk of trusting improperly validated metadata supplied by reverse proxies, load balancers, or other infrastructure components forwarding SMTP connections. Exim 4.100.1 corrects the data-read sizing logic. McCaulay Hudson of watchTowr discovered the bug, which stems from Exim’s use of uninitialized data while processing a Proxy Protocol v2 header. An attacker may c