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Fencer Intel
high 7.5

CVE-2017-17439 json

In Heimdal through 7.4, remote unauthenticated attackers are able to crash the KDC by sending a crafted UDP packet containing empty data fi…

published 2017-12-06 8 y ago modified 2026-06-17 4 mo ago also EUVD-2017-8603

cvss
7.5
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.4%
EPSS 3.4% chance of exploitation in 30 days, percentile 89%
public exploits
0
none known

Summary

In Heimdal through 7.4, remote unauthenticated attackers are able to crash the KDC by sending a crafted UDP packet containing empty data fields for client name or realm. The parser would unconditionally dereference NULL pointers in that case, leading to a segmentation fault. This is related to the _kdc_as_rep function in kdc/kerberos5.c and the der_length_visible_string function in lib/asn1/der_length.c.

Patch / fix

  • heimdal Debian 14, Debian 13, Debian 12 7.5.0+dfsg-1

debian advisories DEBIAN-CVE-2017-17439

  • heimdal Alpine 3.24, Alpine 3.23, Alpine 3.22 +15 more 7.4.0-r2
  • heimdal Alpine 3.6 7.1.0-r2

alpine advisories ALPINE-CVE-2017-17439

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2017-17439 updated cvss 7.5

heimdal: NULL pointer dereference via crafted UDP packets

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.43% chance of exploitation in the next 30 days, higher than 89% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.