Linux: Incorrect Calculation of Buffer Size
CVE-2026-53091 is a high-severity incorrect calculation of buffer size 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 attacker with a low-privileged account, without any action from a user. The record lists versions 5895cfc76924a629c6eaa5e5f049de642860045f, 7564dc804d8289d2e5c6edb8173754051b71bff4, 9d4f5c68f5ad4ab425f3ce1500c97c9f9743999a 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 0.14% 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 5895cfc76924a629c6eaa5e5f049de642860045f or 7564dc804d8289d2e5c6edb8173754051b71bff4 or 9d4f5c68f5ad4ab425f3ce1500c97c9f9743999a or 7fb4c19670110f052c04e1ec1d2b953b9f4f57e4, whichever matches your release line, or a later version.
- Update Linux Kernel to 7.0.10 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | e876f208af18b074f800656e4d1b99da75b2135f up to, but not including, 5895cfc76924a629c6eaa5e5f049de642860045f; e876f208af18b074f800656e4d1b99da75b2135f up to, but not including, 7564dc804d8289d2e5c6edb8173754051b71bff4; e876f208af18b074f800656e4d1b99da75b2135f up to, but not including, 9d4f5c68f5ad4ab425f3ce1500c97c9f9743999a; e876f208af18b074f800656e4d1b99da75b2135f up to, but not including, 7fb4c19670110f052c04e1ec1d2b953b9f4f57e4; 3.16 | 5895cfc76924a629c6eaa5e5f049de642860045f, 7564dc804d8289d2e5c6edb8173754051b71bff4, 9d4f5c68f5ad4ab425f3ce1500c97c9f9743999a, 7fb4c19670110f052c04e1ec1d2b953b9f4f57e4 |
| Red Hat | Red Hat Enterprise Linux 10 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 6 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 7 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9 | Not specified in the record | Not stated |
| Linux | Linux Kernel | 3.16 up to, but not including, 7.0.10 | 7.0.10 |
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
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:H. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.4 | High | CNA |
| CVSS 3.1 | 7.0 | High | CNA |
Official description
In the Linux kernel, the following vulnerability has been resolved: net: pull headers in qdisc_pkt_len_segs_init() Most ndo_start_xmit() methods expects headers of gso packets to be already in skb->head. net/core/tso.c users are particularly at risk, because tso_build_hdr() does a memcpy(hdr, skb->data, hdr_len); qdisc_pkt_len_segs_init() already does a dissection of gso packets. Use pskb_may_pull() instead of skb_header_pointer() to make sure drivers do not have to reimplement this. Some malicious packets could be fed, detect them so that we can drop them sooner with a new SKB_DROP_REASON_SKB_BAD_GSO drop_reason.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Incorrect Calculation of Buffer Size
The product does not correctly calculate the size to be used when allocating a buffer.
How developers prevent this class of flaw
- When allocating a buffer for the purpose of transforming, converting, or encoding an input, allocate enough memory to handle the largest possible encoding. For example, in a routine that converts & characters to & for HTML entity encoding, the output buffer needs to be at least 5 times as large as the input buffer.
- Understand the programming language's underlying representation and how it interacts with numeric calculation (CWE-681). Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions, truncation, conversion and casting between types, not-a-number calculations, and how the language handles numbers that are too large or too small for its underlying representation. Also be careful to account for 32-bit, 64-bit, and other potential differences that may affect the numeric representation.
- Perform input validation on any numeric input by ensuring that it is within the expected range. Enforce that the input meets both the minimum and maximum requirements for the expected range.
More Incorrect Calculation of Buffer Size vulnerabilities (CWE-131)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Third-party and government advisories
- access.redhat.com/security/cve/CVE-2026-53091Third Party Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2492270Third Party Advisory
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53091.jsonThird Party Advisory
Other references
Recent Incorrect Calculation of Buffer Size vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 9.3 Critical severity
- 9.8 Critical severity
- 7.5 High severity
- 9.8 Critical severity
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