Linux: Uncontrolled Recursion
CVE-2026-43185 is a critical-severity uncontrolled recursion 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 1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c, 56eab82fa6fb5ca024b0514e249d40d9b23ee5a7, a110dbe928561d440e9e117d17331139a0bedace 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 0.89% chance of exploitation within 30 days, higher than 60% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c or 56eab82fa6fb5ca024b0514e249d40d9b23ee5a7 or a110dbe928561d440e9e117d17331139a0bedace or ceae058eb707ddd0d68f0872f9d9f23b7c30c37b, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.18.16 or 6.19.6, 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 | 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 56eab82fa6fb5ca024b0514e249d40d9b23ee5a7; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, a110dbe928561d440e9e117d17331139a0bedace; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, ceae058eb707ddd0d68f0872f9d9f23b7c30c37b; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 55abc475d096da4a5356b6efb0cfdc6156bc1550; 0626e6641f6b467447c81dd7678a69c66f7746cf up to, but not including, 6b4f875aac344cdd52a1f34cc70ed2f874a65757; 5.15 | 1c268fd2f59dc9ccb2c2a7d1f439b232dbe1c06c, 56eab82fa6fb5ca024b0514e249d40d9b23ee5a7, a110dbe928561d440e9e117d17331139a0bedace, ceae058eb707ddd0d68f0872f9d9f23b7c30c37b, 55abc475d096da4a5356b6efb0cfdc6156bc1550, 6b4f875aac344cdd52a1f34cc70ed2f874a65757 |
| Linux | Linux Kernel | 5.15 up to, but not including, 6.18.16; 6.19 up to, but not including, 6.19.6; 7.0 | 6.18.16, 6.19.6 |
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: ksmbd: fix signededness bug in smb_direct_prepare_negotiation() smb_direct_prepare_negotiation() casts an unsigned __u32 value from sp->max_recv_size and req->preferred_send_size to a signed int before computing min_t(int, ...). A maliciously provided preferred_send_size of 0x80000000 will return as smaller than max_recv_size, and then be used to set the maximum allowed alowed receive size for the next message. By sending a second message with a large value (>1420 bytes) the attacker can then achieve a heap buffer overflow. This fix replaces min_t(int, ...) with min_t(u32)
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Uncontrolled Recursion
The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.
How developers prevent this class of flaw
- Ensure that an end condition will be reached under all logic conditions. The end condition may include checking against the depth of recursion and exiting with an error if the recursion goes too deep. The complexity of the end condition contributes to the effectiveness of this action.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
Recent Uncontrolled Recursion vulnerabilities
- 7.5 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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