xfrm: Check for underflow in xfrm_state_mtu
Noroxi assessment
Priority: Monitor (action score 31/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.14% (FIRST EPSS).
- Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
- Fixed version: Linux Linux 1021d2877b689a648b27815c854557a917122e93, 2a41b1b31c61c52b972278ce1732a1443f5e89ed, 3db50ceeacb52806d8fe86fb1dfe944df0b9f789.
Low priority for now. Upgrade to Linux Linux 1021d2877b689a648b27815c854557a917122e93, 2a41b1b31c61c52b972278ce1732a1443f5e89ed, 3db50ceeacb52806d8fe86fb1dfe944df0b9f789 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
In the Linux kernel, the following vulnerability has been resolved: xfrm: Check for underflow in xfrm_state_mtu Leo Lin reported OOB write issue in esp component: xfrm_state_mtu() returns u32 but performs its arithmetic in unsigned modulo-2^32 space using an attacker-influenced "header_len + authsize + net_adj" subtracted from a small "mtu" argument. A nobody user can install an IPv4 ESP tunnel SA with a large authentication key (XFRMA_ALG_AUTH_TRUNC, e.g. hmac(sha512), 64-byte key, 64-byte trunc), configure a small interface MTU (68 bytes), and set XFRMA_TFCPAD to a large value. When a single UDP datagram is then sent through the tunnel, xfrm_state_mtu() underflows to a near-2^32 value, and esp_output() consumes it as a signed int via: padto = min(x->tfcpad, xfrm_state_mtu(x, mtu_cached)) esp.tfclen = padto - skb->len (assigned to int) esp.tfclen ends up negative (e.g. -207). It is sign-extended to size_t when passed to memset() inside esp_output_fill_trailer(), producing a ~16 EB write of zeroes at skb_tail_pointer(skb). KASAN logs it as "Write of size 18446744073709551537 at addr ffff888...". Check for underflow and return 1. This causes the sendmsg attempt to fail with ENETUNREACH.
- Published
- Jul 19, 2026
- Updated
- Oct 19, 2026
- EPSS
- 0.1% · 3th percentile
- CWE
- CWE-787
Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.1%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · Linux
- 7.8
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- linux linux kernel2.6.22 and later · before 5.10.259
- linux linux kernel5.11 and later · before 5.15.210
- linux linux kernel5.16 and later · before 6.1.176
- linux linux kernel6.2 and later · before 6.6.143
- linux linux kernel6.7 and later · before 6.12.93
- linux linux kernel6.13 and later · before 6.18.35
- linux linux kernel6.19 and later · before 7.0.12
- linux linux kernel7.1
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.
Linux Linux
- 2.6.22affected
- c5c2523893747f88a83376abad310c8ad13f7197 and later · before 8014f70c4e6e5ab101ae3860a614e65e988372e3affected · git
- c5c2523893747f88a83376abad310c8ad13f7197 and later · before 1021d2877b689a648b27815c854557a917122e93affected · git
- c5c2523893747f88a83376abad310c8ad13f7197 and later · before 2a41b1b31c61c52b972278ce1732a1443f5e89edaffected · git
- c5c2523893747f88a83376abad310c8ad13f7197 and later · before fccd685b32df5aaf6bad4381eeda216468e283f0affected · git
- c5c2523893747f88a83376abad310c8ad13f7197 and later · before 820e501be8aee4b365d218d83227b314309c5fdaaffected · git
- c5c2523893747f88a83376abad310c8ad13f7197 and later · before 82ac903e0b519849647657b8c48d21237ada06a2affected · git
- c5c2523893747f88a83376abad310c8ad13f7197 and later · before 3db50ceeacb52806d8fe86fb1dfe944df0b9f789affected · git
- c5c2523893747f88a83376abad310c8ad13f7197 and later · before 742b04d0550b0ec89dcbc99537ec88653bd1ad90affected · git
- before 2.6.22not affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | linux | before 6.1.176-1 | 6.1.176-1 |
| Debian:13 | linux | before 6.12.94-1 | 6.12.94-1 |
| Debian:14 | linux | before 7.0.12-1 | 7.0.12-1 |
| openSUSE:Leap 16.0 | dtb-aarch64 | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-64kb | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-azure | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-default | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-default-base | before 6.12.0-160000.39.1.160000.2.25 | 6.12.0-160000.39.1.160000.2.25 |
| openSUSE:Leap 16.0 | kernel-docs | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-kvmsmall | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-obs-build | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-obs-qa | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-rt | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-source | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-syms | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
| openSUSE:Leap 16.0 | kernel-zfcpdump | before 6.12.0-160000.39.1 | 6.12.0-160000.39.1 |
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV89Now
- CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
- CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV83Now
Published before and after this one in the same product
- ← EarlierCVE-2026-64007Jul 19, 2026 · netfilter: synproxy: refresh tcphdr after skb_ensure_writable39Monitor
- ← EarlierCVE-2026-64008Jul 19, 2026 · accel/rocket: fix UAF via dangling GEM handle in create_bo31Monitor
- Later →CVE-2026-64010Jul 19, 2026 · nfc: llcp: Fix use-after-free race in nfc_llcp_recv_cc()35Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 1021d2877b689a648b27815c854557a917122e93 | Vendor (CNA) |
| Linux Linux | 2a41b1b31c61c52b972278ce1732a1443f5e89ed | Vendor (CNA) |
| Linux Linux | 3db50ceeacb52806d8fe86fb1dfe944df0b9f789 | Vendor (CNA) |
| Linux Linux | 742b04d0550b0ec89dcbc99537ec88653bd1ad90 | Vendor (CNA) |
| Linux Linux | 8014f70c4e6e5ab101ae3860a614e65e988372e3 | Vendor (CNA) |
| Linux Linux | 820e501be8aee4b365d218d83227b314309c5fda | Vendor (CNA) |
| Linux Linux | 82ac903e0b519849647657b8c48d21237ada06a2 | Vendor (CNA) |
| Linux Linux | fccd685b32df5aaf6bad4381eeda216468e283f0 | Vendor (CNA) |
| debian:linux | 6.1.176-1 · Debian:12 | Package registry (OSV) |
| opensuse:dtb-aarch64 | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-64kb | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-azure | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-default | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-default-base | 6.12.0-160000.39.1.160000.2.25 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-docs | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-kvmsmall | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-obs-build | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-obs-qa | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-rt | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-source | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
| opensuse:kernel-syms | 6.12.0-160000.39.1 · openSUSE:Leap 16.0 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-787 · Out-of-bounds WriteCVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- SSVC exploitation— → none
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (7 more)Show less
- git.kernel.org/stable/c/2a41b1b31c61c52b972278ce1732a1443f5e89ed
- git.kernel.org/stable/c/3db50ceeacb52806d8fe86fb1dfe944df0b9f789
- git.kernel.org/stable/c/742b04d0550b0ec89dcbc99537ec88653bd1ad90
- git.kernel.org/stable/c/8014f70c4e6e5ab101ae3860a614e65e988372e3
- git.kernel.org/stable/c/820e501be8aee4b365d218d83227b314309c5fda
- git.kernel.org/stable/c/82ac903e0b519849647657b8c48d21237ada06a2
- git.kernel.org/stable/c/fccd685b32df5aaf6bad4381eeda216468e283f0
Vendor advisories and official records. Exploit/PoC links are deliberately left out.