Linux: NULL Pointer Dereference
CVE-2026-52986 is a critical-severity NULL pointer dereference vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 8cd0358379570003659186706e077929d6930c40, 9c6afcb1c3cbb2c0da65b8515ac14d7273872f84, b3264c977e79d8a25778d4fd11520f00fea1329c as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.63% chance of exploitation within 30 days, higher than 51% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 8cd0358379570003659186706e077929d6930c40 or 9c6afcb1c3cbb2c0da65b8515ac14d7273872f84 or b3264c977e79d8a25778d4fd11520f00fea1329c or ea2ecd29b8f4433e52607192ca91084f95787ca0, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.258 or 5.15.209 or 6.1.175 or 6.6.141, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 05e3ced297fe755093140e7487e292fb7603316e up to, but not including, 8cd0358379570003659186706e077929d6930c40; 05e3ced297fe755093140e7487e292fb7603316e up to, but not including, 9c6afcb1c3cbb2c0da65b8515ac14d7273872f84; 05e3ced297fe755093140e7487e292fb7603316e up to, but not including, b3264c977e79d8a25778d4fd11520f00fea1329c; 05e3ced297fe755093140e7487e292fb7603316e up to, but not including, ea2ecd29b8f4433e52607192ca91084f95787ca0; 05e3ced297fe755093140e7487e292fb7603316e up to, but not including, 9f69c323ae0ab517e595c2cc74e0ae0d9d085611; 05e3ced297fe755093140e7487e292fb7603316e up to, but not including, 7df9863bf538a626e8a684e59cb2c43eac0ef3c8; 05e3ced297fe755093140e7487e292fb7603316e up to, but not including, 523762e3b6933fff81f01dfa3c60c0774044cdab; 05e3ced297fe755093140e7487e292fb7603316e up to, but not including, 8cf6809cddcbe301aedfc6b51bcd4944d45795f6; and 1 more ranges | 8cd0358379570003659186706e077929d6930c40, 9c6afcb1c3cbb2c0da65b8515ac14d7273872f84, b3264c977e79d8a25778d4fd11520f00fea1329c, ea2ecd29b8f4433e52607192ca91084f95787ca0, 9f69c323ae0ab517e595c2cc74e0ae0d9d085611, 7df9863bf538a626e8a684e59cb2c43eac0ef3c8 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 2.6.26 up to, but not including, 5.10.258; 5.11 up to, but not including, 5.15.209; 5.16 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.141; 6.7 up to, but not including, 6.12.91; 6.13 up to, but not including, 6.18.33; 6.19 up to, but not including, 7.0.10; 7.1 | 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
Official 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]>.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: NULL Pointer Dereference
The product dereferences a pointer that it expects to be valid but is NULL.
How developers prevent this class of flaw
- For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
- Select a programming language that is not susceptible to these issues.
- Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/523762e3b6933fff81f01dfa3c60c0774044cdab
- git.kernel.org/stable/c/7df9863bf538a626e8a684e59cb2c43eac0ef3c8
- git.kernel.org/stable/c/8cd0358379570003659186706e077929d6930c40
- git.kernel.org/stable/c/8cf6809cddcbe301aedfc6b51bcd4944d45795f6
- git.kernel.org/stable/c/9c6afcb1c3cbb2c0da65b8515ac14d7273872f84
- git.kernel.org/stable/c/9f69c323ae0ab517e595c2cc74e0ae0d9d085611
- git.kernel.org/stable/c/b3264c977e79d8a25778d4fd11520f00fea1329c
- git.kernel.org/stable/c/ea2ecd29b8f4433e52607192ca91084f95787ca0
Other references
Recent NULL Pointer Dereference vulnerabilities
- 7.8 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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