netfilter: nf_conntrack_sip: don’t use simple_strtoul_CVE-2026-52986

9.8 / 10

CRITICAL

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

Description

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_conntrack_sip: don't use simple_strtoul

Replace unsafe port parsing in epaddr_len(), ct_sip_parse_header_uri(),
and ct_sip_parse_request() with a new sip_parse_port() helper that
validates each digit against the buffer limit, eliminating the use of
simple_strtoul() which assumes NUL-terminated strings.

The previous code dereferenced pointers without bounds checks after
sip_parse_addr() and relied on simple_strtoul() on non-NUL-terminated
skb data. A port that reaches the buffer limit without a trailing
character is also rejected as malformed.

Also get rid of all simple_strtoul() usage in conntrack, prefer a
stricter version instead. There are intentional changes:

- Bail out if number is > UINT_MAX and indicate a failure, same for
too long sequences.
While we do accept 05535 as port 5535, we will not accept e.g.
'sip:10.0.0.1:005060'. While its syntactically valid under RFC 3261,
we should restrict this to not waste cycles when presented with
malformed packets with 64k '0' characters.

- Force base 10 in ct_sip_parse_numerical_param(). This is used to fetch
'expire=' and 'rports='; both are expected to use base-10.

- In nf_nat_sip.c, only accept the parsed value if its within the 1k-64k
range.

- epaddr_len now returns 0 if the port is invalid, as it already does
for invalid ip addresses. This is intentional. nf_conntrack_sip
performs lots of guesswork to find the right parts of the message
to parse. Being stricter could break existing setups.
Connection tracking helpers are designed to allow traffic to
pass, not to block it.

Based on an earlier patch from Jenny Guanni Qu <[email protected]>.

AI Analysis

AI processing failed - invalid JSON response

Basic Information

ID CVE-2026-52986

Source Linux

Published Jun 24, 2026 at 16:29

Modified Jun 28, 2026 at 06:37

Affected Product

Vendor Linux

Product Linux

Version 05e3ced297fe755093140e7487e292fb7603316e

Affected Versions Linux Linux 05e3ced297fe755093140e7487e292fb7603316e
Linux Linux 05e3ced297fe755093140e7487e292fb7603316e
Linux Linux 05e3ced297fe755093140e7487e292fb7603316e
Linux Linux 05e3ced297fe755093140e7487e292fb7603316e
Linux Linux 05e3ced297fe755093140e7487e292fb7603316e
Linux Linux 05e3ced297fe755093140e7487e292fb7603316e
Linux Linux 05e3ced297fe755093140e7487e292fb7603316e
Linux Linux 05e3ced297fe755093140e7487e292fb7603316e
Linux Linux 2.6.26

References

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_sip: don't use simple_strtoul\n\nReplace unsafe port parsing in epaddr_len(), ct_sip_parse_header_uri(),\nand ct_sip_parse_request() with a new sip_parse_port() helper that\nvalidates each digit against the buffer limit, eliminating the use of\nsimple_strtoul() which assumes NUL-terminated strings.\n\nThe previous code dereferenced pointers without bounds checks after\nsip_parse_addr() and relied on simple_strtoul() on non-NUL-terminated\nskb data. A port that reaches the buffer limit without a trailing\ncharacter is also rejected as malformed.\n\nAlso get rid of all simple_strtoul() usage in conntrack, prefer a\nstricter version instead.  There are intentional changes:\n\n- Bail out if number is > UINT_MAX and indicate a failure, same for\n  too long sequences.\n  While we do accept 05535 as port 5535, we will not accept e.g.\n  'sip:10.0.0.1:005060'.  While its syntactically valid under RFC 3261,\n  we should restrict this to not waste cycles when presented with\n  malformed packets with 64k '0' characters.\n\n- Force base 10 in ct_sip_parse_numerical_param(). This is used to fetch\n  'expire=' and 'rports='; both are expected to use base-10.\n\n- In nf_nat_sip.c, only accept the parsed value if its within the 1k-64k\n  range.\n\n- epaddr_len now returns 0 if the port is invalid, as it already does\n  for invalid ip addresses.  This is intentional. nf_conntrack_sip\n  performs lots of guesswork to find the right parts of the message\n  to parse.  Being stricter could break existing setups.\n  Connection tracking helpers are designed to allow traffic to\n  pass, not to block it.\n\nBased on an earlier patch from Jenny Guanni Qu <[email protected]>.",
    "published": "2026-06-24T16:29:00.752Z",
    "modified": "2026-06-28T06:37:38.888Z",
    "type": "cve",
    "title": "netfilter: nf_conntrack_sip: don't use simple_strtoul",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/8cd0358379570003659186706e077929d6930c40\nhttps://git.kernel.org/stable/c/9c6afcb1c3cbb2c0da65b8515ac14d7273872f84\nhttps://git.kernel.org/stable/c/b3264c977e79d8a25778d4fd11520f00fea1329c\nhttps://git.kernel.org/stable/c/ea2ecd29b8f4433e52607192ca91084f95787ca0\nhttps://git.kernel.org/stable/c/9f69c323ae0ab517e595c2cc74e0ae0d9d085611\nhttps://git.kernel.org/stable/c/7df9863bf538a626e8a684e59cb2c43eac0ef3c8\nhttps://git.kernel.org/stable/c/523762e3b6933fff81f01dfa3c60c0774044cdab\nhttps://git.kernel.org/stable/c/8cf6809cddcbe301aedfc6b51bcd4944d45795f6",
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