Linux: Out-of-bounds Write
CVE-2026-64552 is a high-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 8.4 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists versions f9451d0fd5ba635dcabb49bfe456a6db734a8986, 38e94d63e29f4a5c6eae87ee2c02101aaa321502, fbeb65154583879d556ea94cb2f15888e9470f3d 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 0.15% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to f9451d0fd5ba635dcabb49bfe456a6db734a8986 or 38e94d63e29f4a5c6eae87ee2c02101aaa321502 or fbeb65154583879d556ea94cb2f15888e9470f3d or c7fc9adf4e006155f7f2aeda052fbcde25cdcc49, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.178 or 6.6.145 or 6.12.97 or 6.18, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 82f9028e83944a9eee5229cbc6fee9be1de8a62d up to, but not including, f9451d0fd5ba635dcabb49bfe456a6db734a8986; 946dec89c41726b94d31147ec528b96af0be1b5a up to, but not including, 38e94d63e29f4a5c6eae87ee2c02101aaa321502; 82fe78065450d2d07f36a22e2b6b44955cf5ca5b up to, but not including, fbeb65154583879d556ea94cb2f15888e9470f3d; 0c716703965ffc5ef4311b65cb5d84a703784717 up to, but not including, c7fc9adf4e006155f7f2aeda052fbcde25cdcc49; 0c716703965ffc5ef4311b65cb5d84a703784717 up to, but not including, e6b8463b7d791f3886d7584259d6e9f06a69f12e; 0c716703965ffc5ef4311b65cb5d84a703784717 up to, but not including, 9e5ad06ea826322ce8c58b4a68442a96f600c3c4; 3e9d89f2ecd3636bd4cbdfd0b2dfdaf58f9882e2; 6.1.159 up to, but not including, 6.1.178; and 4 more ranges | f9451d0fd5ba635dcabb49bfe456a6db734a8986, 38e94d63e29f4a5c6eae87ee2c02101aaa321502, fbeb65154583879d556ea94cb2f15888e9470f3d, c7fc9adf4e006155f7f2aeda052fbcde25cdcc49, e6b8463b7d791f3886d7584259d6e9f06a69f12e, 9e5ad06ea826322ce8c58b4a68442a96f600c3c4 |
| 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 | 6.1.159 up to, but not including, 6.1.178; 6.6.117 up to, but not including, 6.6.145; 6.12.58 up to, but not including, 6.12.97; 6.17.8 up to, but not including, 6.18; 6.18.1 up to, but not including, 6.18.40; 6.19 up to, but not including, 7.1.5; 6.18 | 6.1.178, 6.6.145, 6.12.97, 6.18, 6.18.40, 7.1.5 |
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
- LocalThe attacker needs local access or must trick a user into running something.
- 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:L/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: virtio-net: fix len check in receive_big() receive_big() bounds the device-announced length by (big_packets_num_skbfrags + 1) * PAGE_SIZE. That is still too loose: add_recvbuf_big() sets sg[1] to start at offset sizeof(struct padded_vnet_hdr) into the first page, so the chain actually carries hdr_len + (PAGE_SIZE - sizeof(padded_vnet_hdr)) + big_packets_num_skbfrags * PAGE_SIZE bytes -- 20 bytes less than the check allows for the common hdr_len == 12 case. A malicious virtio backend can announce a len in that gap. page_to_skb() then walks one frag past the page chain, storing a NULL page->private into skb_shinfo()->frags[MAX_SKB_FRAGS], which is both an out-of-bounds write past the static frag array and a NULL frag handed up the rx path. Bound len by the size add_recvbuf_big() actually advertised.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/38e94d63e29f4a5c6eae87ee2c02101aaa321502
- git.kernel.org/stable/c/9e5ad06ea826322ce8c58b4a68442a96f600c3c4
- git.kernel.org/stable/c/c7fc9adf4e006155f7f2aeda052fbcde25cdcc49
- git.kernel.org/stable/c/e6b8463b7d791f3886d7584259d6e9f06a69f12e
- git.kernel.org/stable/c/f9451d0fd5ba635dcabb49bfe456a6db734a8986
- git.kernel.org/stable/c/fbeb65154583879d556ea94cb2f15888e9470f3d
Third-party and government advisories
- cert-portal.siemens.com/productcert/html/ssa-019113.htmlThird Party Advisory
- cert-portal.siemens.com/productcert/html/ssa-457936.htmlThird Party Advisory
Recent Out-of-bounds Write vulnerabilities
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
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