CVE-2026-45185: Use-After-Free (CVSS 9.8)

Description

Exim before 4.99.3, in certain GnuTLS configurations, has a remotely reachable use-after-free in the BDAT body parsing path. It is triggered when a client sends a TLS close_notify mid-body during a CHUNKING transfer, followed by a final cleartext byte on the same TCP connection. This can lead to heap corruption. An unauthenticated network attacker exploiting this vulnerability could execute arbitrary code.

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CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0008

Probability of exploitation

0.24%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-416 Use After Free

References

Other References

https://code.exim.org/exim/wiki/wiki/EximSecurity https://exim.org https://exim.org/static/doc/security/CVE-2026-45185.txt https://exim.org/static/doc/security/EXIM-Security-2026-05-01.1/ https://news.ycombinator.com/item?id=48111748 https://www.openwall.com/lists/oss-security/2026/05/12/4 https://xbow.com/blog/dead-letter-cve-2026-45185-xbow-found-rce-exim http://www.openwall.com/lists/oss-security/2026/05/12/25

Frequently Asked Questions

What is CVE-2026-45185? +

Exim before 4.99.3, in certain GnuTLS configurations, has a remotely reachable use-after-free in the BDAT body parsing path. It is triggered when a client sends a TLS close_notify mid-body during a CHUNKING transfer, followed by a final cleartext byte on the same TCP connection. This can lead to heap corruption. An unauthenticated network attacker exploiting this vulnerability could execute arbitrary code. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-45185? +

CVE-2026-45185 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0008, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-45185? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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