PatchTheCVECVE-2019-19977: libESMTP through 1.0.6 mishandles domain copying into a fixed-size buffer in ntlm_build_type_2 in ntlm/ntlmstr
CVE-2019-19977 is a critical-severity flaw (CVSS 9.8) affecting libesmtp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
libESMTP through 1.0.6 mishandles domain copying into a fixed-size buffer in ntlm_build_type_2 in ntlm/ntlmstruct.c, as demonstrated by a stack-based buffer over-read.
Why this priority
- Critical severity
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 3.0% (top 13%) |
| CISA exploited list | No |
| Weakness | CWE-125 |
| Published | 2019-12-26 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2019-19977?
libesmtp: upgrade to newer than 1.0.6. Exact commands for each OS are on this page.
Is CVE-2019-19977 being exploited?
CVE-2019-19977 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2019-19977 affect?
CVE-2019-19977 affects libesmtp. Severity is critical (CVSS 9.8). libESMTP through 1.0.6 mishandles domain copying into a fixed-size buffer in ntlm_build_type_2 in ntlm/ntlmstruct.c, as demonstrated by a stack-based buffer over-read.
How urgent is CVE-2019-19977?
Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action