Linux: Integer Overflow or Wraparound
CVE-2026-31649 is a critical-severity integer overflow or wraparound 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 513e06735f5be575b409d195822195348b164e48, 275bdf762e82082f064e60a92448fa2ac43cf95b, a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f 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 0.46% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 513e06735f5be575b409d195822195348b164e48 or 275bdf762e82082f064e60a92448fa2ac43cf95b or a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f or b7b8012193fd98236d7ae05d4b553f010a77b2ef, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.169 or 6.6.135, 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 | 286a837217204b1ef105e3a554d0757e4fdfaac1 up to, but not including, 513e06735f5be575b409d195822195348b164e48; 286a837217204b1ef105e3a554d0757e4fdfaac1 up to, but not including, 275bdf762e82082f064e60a92448fa2ac43cf95b; 286a837217204b1ef105e3a554d0757e4fdfaac1 up to, but not including, a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f; 286a837217204b1ef105e3a554d0757e4fdfaac1 up to, but not including, b7b8012193fd98236d7ae05d4b553f010a77b2ef; 286a837217204b1ef105e3a554d0757e4fdfaac1 up to, but not including, 2c91b39912278d0878f9ba60ba04d2518b18a08d; 286a837217204b1ef105e3a554d0757e4fdfaac1 up to, but not including, 6fca757c20396dc2e604dcc61922264e9e3dc803; 286a837217204b1ef105e3a554d0757e4fdfaac1 up to, but not including, 10d12b9240ebf96c785f0e2e4228318cd5f3a3eb; 286a837217204b1ef105e3a554d0757e4fdfaac1 up to, but not including, 51f4e090b9f87b40c21b6daadb5c06e6c0a07b67; and 1 more ranges | 513e06735f5be575b409d195822195348b164e48, 275bdf762e82082f064e60a92448fa2ac43cf95b, a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f, b7b8012193fd98236d7ae05d4b553f010a77b2ef, 2c91b39912278d0878f9ba60ba04d2518b18a08d, 6fca757c20396dc2e604dcc61922264e9e3dc803 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 and later; V3.1.5 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; V3.1.5 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; V3.1.5 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; V3.1.5 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; V3.1.5 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 3.2.1 up to, but not including, 5.10.253; 5.11 up to, but not including, 5.15.203; 5.16 up to, but not including, 6.1.169; 6.2 up to, but not including, 6.6.135; 6.7 up to, but not including, 6.12.82; 6.13 up to, but not including, 6.18.23; 6.19 up to, but not including, 6.19.13; 3.2; and 1 more ranges | 5.10.253, 5.15.203, 6.1.169, 6.6.135, 6.12.82, 6.18.23 |
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: net: stmmac: fix integer underflow in chain mode The jumbo_frm() chain-mode implementation unconditionally computes len = nopaged_len - bmax; where nopaged_len = skb_headlen(skb) (linear bytes only) and bmax is BUF_SIZE_8KiB or BUF_SIZE_2KiB. However, the caller stmmac_xmit() decides to invoke jumbo_frm() based on skb->len (total length including page fragments): is_jumbo = stmmac_is_jumbo_frm(priv, skb->len, enh_desc); When a packet has a small linear portion (nopaged_len <= bmax) but a large total length due to page fragments (skb->len > bmax), the subtraction wraps as an unsigned integer, producing a huge len value (~0xFFFFxxxx). This causes the while (len != 0) loop to execute hundreds of thousands of iterations, passing skb->data + bmax * i pointers far beyond the skb buffer to dma_map_single(). On IOMMU-less SoCs (the typical deployment for stmmac), this maps arbitrary kernel memory to the DMA engine, constituting a kernel memory disclosure and potential memory corruption from hardware. Fix this by introducing a buf_len local variable clamped to min(nopaged_len, bmax). Computing len = nopaged_len - buf_len is then always safe: it is zero when the linear portion fits within a single descriptor, causing the while (len != 0) loop to be skipped naturally, and the fragment loop in stmmac_xmit() handles page fragments afterward.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Integer Overflow or Wraparound
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.
How developers prevent this class of flaw
- Ensure that all protocols are strictly defined, such that all out-of-bounds behavior can be identified simply, and require strict conformance to the protocol.
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. If possible, choose a language or compiler that performs automatic bounds checking.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Use libraries or frameworks that make it easier to handle numbers without unexpected consequences. Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++).
More Integer Overflow or Wraparound vulnerabilities (CWE-190)
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/10d12b9240ebf96c785f0e2e4228318cd5f3a3eb
- git.kernel.org/stable/c/275bdf762e82082f064e60a92448fa2ac43cf95b
- git.kernel.org/stable/c/2c91b39912278d0878f9ba60ba04d2518b18a08d
- git.kernel.org/stable/c/513e06735f5be575b409d195822195348b164e48
- git.kernel.org/stable/c/51f4e090b9f87b40c21b6daadb5c06e6c0a07b67
- git.kernel.org/stable/c/6fca757c20396dc2e604dcc61922264e9e3dc803
- git.kernel.org/stable/c/a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f
- git.kernel.org/stable/c/b7b8012193fd98236d7ae05d4b553f010a77b2ef
Other references
Recent Integer Overflow or Wraparound vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
- 7.8 High severity
- 9.8 Critical severity
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