Skip to content
Noroxi
CVE-2006-4434· NVD / CVE Program· CNA mitre

Use-after-free vulnerability in Sendmail before 8.13.8 allows remote attackers to cause a denial of service (crash) via a long "header line"

Use-after-free vulnerability in Sendmail before 8.13.8 allows remote attackers to cause a denial of service (crash) via a long "header line", which causes a previously freed variable to be referenced. NOTE: the original developer has disputed the severity of this issue, saying "The only denial of service that is possible here is to fill up the disk with core dumps if the OS actually generates different core dumps (which is unlikely)... the bug is in the shutdown code (finis()) which leads directly to exit(3), i.e., the process would terminate anyway, no mail delivery or receiption is affected."

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Aug 28, 2006
Updated
Jun 16, 2026
EPSS
4.5% · 91th percentile
Follow this CVE

Sign in to follow · You’ll be notified if a followed record enters KEV, gets an exploit or is updated.

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 4.5%

Affected systems

VendorProduct
sendmailsendmail

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • sendmail sendmailbefore 8.13.8

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12sendmailbefore 8.13.8-18.13.8-1
Debian:3.1sendmailbefore 8.13.4-3sarge38.13.4-3sarge3

Same product

sendmail: all records

Other highest-scoring records for the same primary product.

  • CVE-2002-1337Buffer overflow in Sendmail 5.79 to 8.12.7 allows remote attackers to execute arbitrary code via certain formatted address fields, related t
    62This week
  • CVE-2003-0161The prescan() function in the address parser (parseaddr.c) in Sendmail before 8.12.9 does not properly handle certain conversions from char
    52Plan
  • CVE-2006-0058Signal handler race condition in Sendmail 8.13.x before 8.13.6 allows remote attackers to execute arbitrary code by triggering timeouts in a
    39Monitor
  • CVE-2009-4565sendmail before 8.14.4 does not properly handle a '\0' character in a Common Name (CN) field of an X.509 certificate, which (1) allows man-i
    31Monitor
  • CVE-2002-2261Sendmail 8.9.0 through 8.12.6 allows remote attackers to bypass relaying restrictions enforced by the 'check_relay' function by spoofing a b
    31Monitor
  • CVE-2002-0906Buffer overflow in Sendmail before 8.12.5, when configured to use a custom DNS map to query TXT records, allows remote attackers to cause a
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:sendmail8.13.8-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

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

nvd-primary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

c
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);

Fixed

c
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records